Administration of tlr7 ligands and prodrugs thereof for treatment of infection by hepatitis c virus

ABSTRACT

This invention relates to methods for treating or preventing hepatitis C virus infections in mammals using Toll-Like Receptor (TLR)7 ligands and prodrugs thereof. More particularly, this invention relates to methods of orally administering a therapeutically effective amount of one or more prodrugs of TLR7 ligands for the treatment or prevention of hepatitis C viral infection. Oral administration of these TLR7 immunomodulating ligands and prodrugs thereof to a mammal provides therapeutically effective amounts and reduced undesirable side effects.

This application is a divisional application of and claims priority toU.S. patent application Ser. No. 10/931,130 filed Sep. 1, 2004, whichclaims the benefit of U.S. Provisional Application No. 60/500,339, filedSep. 5, 2003, U.S. Provisional Application No. 60/518,996, filed Nov.10, 2003, and U.S. Provisional Application No. 60/518,997, filed Nov.10, 2003.

1. FIELD OF THE INVENTION

This invention relates to methods for treating or preventing hepatitis Cvirus infections in mammals using Toll-Like Receptor (TLR)7 ligands andprodrugs thereof. More particularly, this invention relates to methodsof orally administering a therapeutically effective amount of one ormore prodrugs of TLR7 ligands for the treatment or prevention ofhepatitis C viral infection. Oral administration of these TLR7immunomodulating ligands and prodrugs thereof to a mammal providestherapeutically effective amounts and reduced undesirable side effects.

2. BACKGROUND OF THE INVENTION

Immunomodulation by small molecules can be achieved by identifyingcompounds that bind and activate Toll-Like Receptors (TLRs). TLRs playan important role in innate immune responses in mammals and are oftenthe first line of defense against pathogens such as bacteria andviruses. The various TLRs vary in their abundance in different mammaliancell types and also vary regarding the molecular structures that bindthe TLR and activate signaling pathways. These signaling pathways leadto the range of responses associates with innate immunity.

TLRs detect PAMPs (pathogen-associated molecular patterns) and stimulateimmune cells via the MyD88-dependent interleukin 1 receptor (IL-1R)-TLRsignaling pathway, which leads to activation of the transcription factorNF-κB2. Ten functional family members of TLRs (TLR1 to TLR10) have beenidentified in humans. Akira S. et al., Nature Immunol., 2, 675-680(2001). TLR2, TLR4, and TLR5 are crucial for the recognition ofpeptidoglycan, lipopolysacharide, and flagellin. Hayashi, F. et al.,Nature, 410, 1099-1103 (2001). TLR6 associates with TLR2 and recognizeslipoproteins from mycoplasma. Ozinsky, A., et al., Proc. Natl. Acad.Sci. USA., 97, 13766-13771 (2000). TLR9 detects bacterial DNA containingunmethylated CpG motifs and TLR3 activates immune cells in response todouble-stranded RNA. Hemmi, H. et al., Nature, 408, 740-745 (2000).

A number of compounds, including guanosine analogs, substitutedpyrimidines, and imidazoquinolines have been reported as ligands forTLR7. See, e.g., Hemmi et al., Nature Immunol., 3, 196-200 (2002)(imiquimod and R-848 (resiquimod)); Jurk et al., Nat. Immunol., 3, 499(2002) (R-848); and Lee et al., Proc. Natl. Acad. Sci. USA, 100,6646-6651 (2003) (wherein guanosine analogs loxoribine,7-thia-8-oxoguanosine (isatoribine), and 7-deazaguanosine, and theimidazoquinolines imiquimod and R-848 (resiquimod) selectively activateTLR7).

Prior to being linked as potential TLR7 ligands, guanosine analogs andother D- and L-purine nucleosides have been the subject of considerableresearch the past two decades. See, e.g., Reitz et al., J. Med. Chem.,37, 3561-78 (1994); Michael et al., J. Med. Chem., 36, 3431-36 (1993)(immunomodulatory guanosine analogs having substituents at the 7- and/or8-positions); U.S. Pat. No. 5,821,236 to Krenitsky et al. (disclosing6-alkoxy derivatives of arabinofuranosyl purine derivatives that areuseful for tumor therapy); U.S. Pat. No. 5,041,426 to Robins et al.(certain pyrimido[4,5-d]pyridimine nucleosides are disclosed in as beingeffective in treatment against L1210 in BDF1 mice); Revankar et al., J.Med. Chem., 27, 1489-96 (1984) (3-Deazaguanine nucleosides andnucleotides demonstrating significant broad spectrum antiviral activityagainst certain DNA and RNA viruses);

A number of compounds known to be immunostimulants have recently beenidentified in the literature as TLR7 ligands, see, e.g., Heil et al.,Eur. J. Immunol., 33(11), 2987-97 (2003), Lore et al., J. Immunol.,171(8), 4320-8 (2003), Nagase et al., J. Immunol., 171(8), 3977-82(2003), Mohty et al., J. Immunol., 171(7), 3385-93 (2003),Pinhal-Enfield, et al., Am. J. Pathol., 163(2), 711-21 (2003), Doxsee etal, J. Immunol., 171(3), 1156-63 (2003), Bottcher et al., Neurosci.Lett., 344(1), 17-20 (2003), Kaisho et al., Curr. Mol. Med., 3(4),373-85 (2003), Okada et al., Eur. J. Immunol., 33(4), 1012-9 (2003),Edwards et al., Eur. J. Immunol, 33(4), 827-33 (2003), Akira et al.,Immunol. Lett., 85(2), 85-95 (2003), Ito et al., Hum. Immunol, 63(12),1120-5 (2002), Rothenfusser et al., Hum. Immunol., 63(12), 1111-9(2002), Yamamoto et al., J. Immunol., 169(12), 6668-72 (2002), Gibson etal., Cell Immunol., 218(1-2), 74-86 (2002), Horng et al., Nature, 420(6913), 329-33 (2002), Yamamoto et al., Nature, 420(6913), 324-9 (2002),Applequist et al., Int. Immunol., 14(9), 1065-74 (2002), Sato et al.,Int. Immunol., 14(7), 783-91 (2002); Jurket et al., Nat. Immunol., 3(6),499 (2002); Hornung et al., J. Immunol., 168(9), 4531-7 (2002), Hemmi etal., Nat. Immunol., 3(2), 196-200 (2002); Bruno et al., Eur. J.Immunol., 31(11), 3403-12 (2001); Jarrossay et al., Eur. J. Immunol.,31(11), 3388-93 (2001); Miettinen et al., Genes Immun., 2(6), 349-55(2001), Chuang et al., Eur. Cytokine Netw., 11(3), 372-8 (2000), and Duet al., Eur. Cytokine Netw., 11(3), 362-71 (2000).

These TLR7 ligands are known to stimulate immune responses in vitro andin animal species, and this has led to testing of the uses of thesecompounds for several therapeutic uses, including antiviral and cancertherapies. These compounds have been characterized as analogs orderivatives of a) guanosine, b) imidazoquinoline, and c) pyrimidine. SeeAkira, Current Opinion, 15, 5-11 (2003). One member (imiquimod) of theimidazoquinoline chemical class has been found effective for treatingtopical genital infections by papilloma virus. A second member of theimidazoquinoline class, resiquimod, has been tested for the treatment ofHCV, but this compound failed to show anti-HCV effect at tolerated oraldoses. Pockros et al., Gastroenterology, 124 (Suppl 1), A-766 (2003).

Thus, while there has been some limited use of TLR7 ligands for thetreatment of immunological disease and viral infections; see, e.g., U.S.Pat. Nos. 5,041,426 and 4,880,784 to Robins et al.(3-β-D-ribofuranosylthiazolo[4,5-d]pyridimines demonstrating significantimmunoactivity, including murine spleen cell proliferation and in vivoactivity against Semliki Forest virus); United States Patent ApplicationPublication No. US 2003/0199461 and WO 03/045968 to Averett et al.(3-β-D-ribofuranosylthiazolo[4,5-d]pyrimidine nucleosides demonstratingactivity against acute and chronic infections of both RNA and DNAviruses); to date ligands have proved ineffective for the treatment orprevention of Hepatitis C virus.

It is also known that the oral administration of many purine nucleosideanalogs are subject to difficulties arising from poor absorption, poorsolubility, or degradation in the digestive tract as a result of acidicor alkaline conditions or the action of enzymes, and/or combinations ofthese phenomena. Thus there remains a need for purine nucleoside analogswith improved oral availability and administration that are used tomodulate aspects of the immune system.

Moreover, immunomodulatory nucleosides have relatively poor oraltolerability when compared to that of the intravenous route. Also, thegastrointestinal tract presents a particular tolerability barrier toimmunologic agents by virtue of the large amount of immune tissueassociated with the intestinal wall (i.e., gut). Although this is animportant biologic mechanism for preventing invasion of the body by gutflora, the immune tissue also may become preferentially affected afteroral administration of immunomodulatory compounds because of the highlocal concentrations of the administered compound in the gut. This leadsto undesirable side effects, for example in the case of immuneactivating agents there is observed gastroenteritis and localizedhemorrhagic effects.

A solution to the problem of effective oral delivery of immunomodulatorsis not evident in the literature. Available evidence indicates thatsystemic levels of administered drugs in this class have been limited bygastrointestinal toxicities arising after low oral doses. Thereforethere remains a need for immunomodulating TLR7 ligands that haveimproved oral availability and reduced gastrointestinal irritancy.

3. SUMMARY OF THE INVENTION 3.1 TLR7 Ligands

This invention encompasses novel methods for the treatment or preventionof hepatitis C viral infection, and novel pharmaceutical compositionswhich utilize TLR7 ligands or pharmaceutically acceptable salts,hydrates, metabolites or stereoisomers thereof.

In one embodiment, the invention encompasses a method of treating orpreventing a hepatitis C virus infection in a patient in need thereofcomprising administering to the patient a therapeutically orprophylactically effective amount of a TLR7 ligand or a pharmaceuticallyacceptable salt, hydrate, metabolite or stereoisomer thereof or apharmaceutically acceptable salt or hydrate of said stereoisomer.

In another embodiment, the invention encompasses a method of treating orpreventing a hepatitis C virus infection in a patient in need thereofcomprising administering to the patient a therapeutically orprophylactically effective amount of a TLR7 ligand selected from analogsand derivatives of a) guanosine b) imidazoquinoline c) adenine, and d)pyrimidine.

In another embodiment, the invention encompasses a method of treating orpreventing a hepatitis C virus infection in a patient in need thereofcomprising administering to the patient a therapeutically orprophylactically effective amount of a TLR7 ligand selected from

wherein:each R¹ is H, or a substituted or unsubstituted alkyl, alkenyl, oralkynyl, which may be interrupted by one or more O, S, or N heteroatoms,or a substituted or unsubstituted aryl or heteroaryl;R² is H, OH, SH, halo, or a substituted or unsubstituted alkyl, alkenyl,or alkynyl, which may be interrupted by one or more O, S, or Nheteroatoms, or a substituted or unsubstituted —O-(alkyl), —O-(aryl),—O-(heteroaryl), —S-(alkyl), —S-(aryl), —S-(heteroaryl), aryl, orheteroaryl;R³ is H, OH, or SH, or a substituted or unsubstituted alkyl, alkenyl,alkynyl, aryl, heteroaryl, —O-(alkyl), —O-(aryl), —O-(heteroaryl),—S-(alkyl), —S-(aryl), —S-(heteroaryl), —NH(alkyl), —NH(aryl),—NH(heteroaryl), —NH(R⁴)(alkyl), —NH(R⁴)(aryl), or —NH(R⁴)(heteroaryl),wherein R⁴ is a substituted or unsubstituted alkyl;

X is O or S;

Y is H, halo, OH, OR⁴, SH, SR⁴, or a substituted or unsubstituted alkylor aryl;Z is H, halo, OH, OR⁴, SH, or SR⁴;or a pharmaceutically acceptable salt, hydrate, metabolite orstereoisomer thereof or a pharmaceutically acceptable salt or hydrate ofsaid stereoisomer.

In another embodiment, the invention encompasses a method of treating orpreventing a hepatitis C virus infection in a patient in need thereofcomprising administering to the patient a therapeutically orprophylactically effective amount of a TLR7 ligand selected from FormulaIa, Ib, Ic, Id, Ie, If, Ig, and Ih, wherein R¹ is H or a substituted orunsubstituted alkyl, alkenyl, or alkynyl; R² is H, OH, halo, or asubstituted or unsubstituted alkyl, alkenyl, or alkynyl, or—CH₂—O-(alkyl); R³ is H, OH, or SH, or a substituted or unsubstituted—O-(alkyl), —S-(alkyl), or —NH(alkyl); X is O or S; Y is H, halo, OH,OR⁴, SH, or SR⁴; and Z is H, halo, OH, OR⁴, SH, or SR⁴.

In another embodiment, the invention encompasses a method of treating orpreventing a hepatitis C virus infection in a patient in need thereofcomprising administering to the patient a therapeutically orprophylactically effective amount of a TLR7 ligand selected from

or a pharmaceutically acceptable salt, hydrate, metabolite orstereoisomer thereof.

In one aspect, the invention encompasses a method for treating orpreventing hepatitis C virus infection in a mammal in need thereof,preferably in a human in need thereof.

In an alternative embodiment, the invention encompasses a method fortreating or preventing hepatitis C virus infection in a patient in needthereof, comprising administering to the patient a therapeutically orprophylactically effective amount of a TLR7 ligand and apharmaceutically acceptable excipient, carrier, or vehicle.

In an alternative embodiment, the invention encompasses a method fortreating or preventing hepatitis C virus infection in a patient in needthereof, comprising administering to the patient a therapeutically orprophylactically effective amount of a TLR7 ligand orally, mucosally,topically or transdermally.

In a preferred embodiment, the invention encompasses a method fortreating or preventing hepatitis C virus infection in a patient in needthereof, comprising administering to the patient a therapeutically orprophylactically effective amount of a TLR7 ligand parenterally.

In a separate embodiment, the invention encompasses a method fortreating or preventing hepatitis C virus infection in a patient in needthereof, comprising administering to the patient a therapeutically orprophylactically effective amount of a TLR7 ligand and an additionaltherapeutic agent, preferably an additional antiviral orimmunomodulatory agent.

The invention also encompasses pharmaceutical compositions suitable forparenteral administration to a patient comprising a therapeutically orpharmaceutically acceptable amount of a TLR7 ligand of the invention ina sterile form; pharmaceutical compositions suitable for oraladministration to a patient comprising a therapeutically orpharmaceutically acceptable amount of a TLR7 ligand of the invention,wherein such compositions are formulated to reduce exposure of thesubepithelial immune anatomy to the TLR7 ligand while improving systemicabsorption of the TLR7 ligand; pharmaceutical compositions suitable formucosal administration to a patient comprising a therapeutically orpharmaceutically acceptable amount of a TLR7 ligand of the invention,wherein such compositions are formulated to reduce exposure of thesubepithelial immune anatomy to the TLR7 ligand while improving systemicabsorption of the TLR7 ligand; and pharmaceutical compositions suitablefor topical administration to a patient comprising a therapeutically orpharmaceutically acceptable amount of a TLR7 ligand of the invention,wherein such compositions are formulated to reduce exposure of thesubepithelial immune anatomy to the TLR7 ligand while improving systemicabsorption of the TLR7 ligand. Depending on the specific tissue to betreated, additional components, such as penetration enhancers, may beused prior to, in conjunction with, or subsequent to treatment withactive ingredients of the invention. In a preferred embodiment, each ofthese compositions is in single unit dosage form and comprising anamount of active ingredient sufficient to treat or prevent humaninfection by hepatitis C virus.

In a specific embodiment, the invention encompasses a pharmaceuticalcomposition comprising a TLR7 ligand selected from analogs andderivatives of a) guanosine, b) imidazoquinoline, c) adenine, and d)pyrimidine.

In another specific embodiment, the invention encompasses apharmaceutical composition comprising a TLR7 ligand selected fromFormulas Ia, Ib, Ic, Id, Ie, If, Ig, and Ih, or a pharmaceuticallyacceptable salt, hydrate, metabolite or stereoisomer thereof or apharmaceutically acceptable salt or hydrate of said stereoisomer.

3.2 TLR7 Ligand Prodrugs

This invention also encompasses novel methods for the treatment orprevention of hepatitis C viral infection, and novel pharmaceuticalcompositions which utilize TLR7 ligand prodrugs or pharmaceuticallyacceptable salts, hydrates, metabolites or stereoisomers thereof.

This invention also encompasses novel methods of treating diseasesresponsive to immuno therapy with immunologic agents, comprising orallyadministering a TLR7 ligand prodrug to a patient in need of immunotherapy, wherein the TLR7 prodrug achieves a therapeutically effectiveplasma concentration of the TLR7 ligand in the patient.

In one embodiment, the invention encompasses a method of treating ahepatitis C virus infection in a patient comprising orally administeringto the patient a TLR7 ligand prodrug or a pharmaceutically acceptablesalt, hydrate, or stereoisomer thereof, wherein the oral administrationof the TLR7 ligand prodrug achieves a therapeutically effective plasmaconcentration of the TLR7 ligand while reducing undesirable side effectsassociated with TLR7 ligands. In a preferred embodiment, the TLR7 ligandprodrug is a masked TLR7 ligand prodrug.

In another embodiment, the invention also encompasses a method oftreating diseases responsive to immuno therapy while reducingundesirable side effects associated with immunologic agents, comprisingorally administering a TLR7 ligand prodrug to a patient in need ofimmuno therapy, wherein the TLR7 prodrug achieves a therapeuticallyeffective plasma concentration of the TLR7 ligand in the patient. In apreferred embodiment, the TLR7 ligand prodrug is a masked TLR7 ligandprodrug.

In another embodiment, the oral administration of the TLR7 ligandprodrug improves the in vivo bioavailability of the TLR7 ligand. In apreferred embodiment, the oral administration of the TLR7 ligand prodrugachieves an in vivo effective plasma concentration of the TLR7 ligandthat is 10% to 500% of the effective in vivo exposure obtained upon oraladministration of the TLR7 ligand alone. In another preferredembodiment, the oral administration of the masked TLR7 ligand prodrugachieves an in vivo effective plasma concentration of the TLR7 ligandthat is 50% to 200% of the effective in vivo exposure obtained upon oraladministration of the TLR7 ligand alone.

In another embodiment, the oral administration of the TLR7 ligandprodrug reduces adverse side effects. In a preferred embodiment, theside effect comprises gastrointestinal irritancy, whereingastrointestinal irritancy comprises hemorrhage, lesions, and emesis.

In another embodiment, the TLR7 ligand prodrug improves oralavailability by at least 25% and reduces gastrointestinal irritancy byat least 50% in a patient relative to the oral administration of theTLR7 ligand alone. In another embodiment, the TLR7 ligand prodrugimproves oral availability by at least 50% and reduces gastrointestinalirritancy by such that other toxicities become limiting in a patientrelative to the oral administration of the TLR7 ligand alone.

In a preferred embodiment, the TLR7 ligand prodrug achieves atherapeutically effective plasma concentration that is 25% to 200% ofthe effective in vivo concentration of the TLR7 ligand in a patientafter oral administration, with minimal gastrointestinal irritancy.

In one embodiment, the methods of the invention encompass administeringto a patient in need thereof a therapeutically or prophylacticallyeffective amount of a prodrug of a TLR7 ligand selected from analogs andderivatives of a) guanosine, b) imidazoquinoline, c) adenine, and d)pyrimidine.

In another embodiment, the methods of the invention encompassadministering to a patient in need thereof a therapeutically orprophylactically effective amount of a prodrug of a TLR7 ligand selectedfrom analogs and derivatives of a) guanosine, b) imidazoquinoline, c)adenine, and d) pyrimidine, wherein the prodrug is an (a) amide,carbamate, or amidine moiety after conversion of a TLR7 ligand aminesubstituent, (b) ester, carbonate, carbamate, ether, imidate, acetal,aminal, or ketal moiety after conversion of a TLR7 ligand alcoholsubstituent, (c) acetal or ketal moiety after conversion of a TLR7ligand keto substituent, (d) imidate moiety after conversion of a TLR7ligand carbonyl of an amido substituent, (e) deoxygenated moiety afterconversion of a TLR7 ligand oxo substituent of pyrimidine or guanosine,or (f) amine.

In another embodiment, the methods of the invention encompassadministering to a patient in need thereof a therapeutically orprophylactically effective amount of a prodrug of a TLR7 ligand selectedfrom

wherein:each R¹ is H, or a substituted or unsubstituted alkyl, alkenyl, oralkynyl, which may be interrupted by one or more O, S, or N heteroatoms,or a substituted or unsubstituted aryl or heteroaryl;R² is H, OH, SH, halo, or a substituted or unsubstituted alkyl, alkenyl,or alkynyl, which may be interrupted by one or more O, S, or Nheteroatoms, or a substituted or unsubstituted —O-(alkyl), —O-(aryl),—O-(heteroaryl), —S-(alkyl), —S-(aryl), —S-(heteroaryl), aryl, orheteroaryl;R³ is H, OH, or SH, or a substituted or unsubstituted alkyl, alkenyl,alkynyl, aryl, heteroaryl, —O-(alkyl), —O-(aryl), —O-(heteroaryl),—S-(alkyl), —S-(aryl), —S-(heteroaryl), —NH(alkyl), —NH(aryl),—NH(heteroaryl), —NH(R⁴)(alkyl), —NH(R⁴)(aryl), or —NH(R⁴)(heteroaryl);R⁴ is a substituted or unsubstituted alkyl;R⁵ is independently H, —C(O)(C₁₋₈alkyl), or a racemic, L-, or D-aminoacid group —C(O)CHNH₂R⁹;

R⁶ is H, OR¹⁰, or N(R¹¹)₂;

R⁷ is independently H or a substituted or unsubstituted—C(O)(C₁₋₁₈alkyl) or —C(O)₂(C₁ ₋₁₈alkyl);R⁸ is H, —OH, —O-(alkyl), —OCO₂(C₁₋₁₈alkyl), —OC(O)(C₁₋₁₈alkyl), or aracemic, L-, or D-amino acid group —OC(O)CHNH₂R¹;R⁹ is H, or a substituted or unsubstituted alkyl, C(O)CH(C₁₋₆ alkyl)NH₂,or —C(O)CH(CH₂-aryl)NH₂;R¹⁰ is independently H, C₁₋₆ alkyl, C₃₋₇ alkenyl, C₃₋₇alkynyl,—(CR¹²R¹³)_(t)(C₆-C₁₀ aryl), —(CR¹²R¹³)_(t)(C₃-C₁₀ cycloalkyl),—(CR¹²R¹³)_(t)(C₄-C₁₀ heterocyclic), —(CR¹²R¹³)_(t>1)OH,—(CR¹²R¹³)_(t>0)CO₂C₁₋₁₈alkyl, and —(CR¹²R¹³)_(t>0)N(R¹⁴)CO₂C₁₋₁₈alkyl,and SO₂(aryl), wherein t is an integer from 0 to 6 unless otherwiseindicated, and wherein the alkyl, alkenyl, alkynyl, aryl, cycloalkyl,and heterocyclic moieties of the foregoing groups are optionallysubstituted with substituents independently selected from halo, cyano,nitro, trifluoromethyl, trifluoromethoxy, C₁-C₆ alkyl, C₂-C₆ alkenyl,C₂-C₆ alkynyl, hydroxy, C₁-C₆ alkoxy, —NH₂, —NH-alkyl, —N(alkyl)₂,—NH-aryl, —N(alkyl)(aryl), —N(aryl)₂, —NHCHO, —NHC(O)alkyl, —NHC(O)aryl,—N(alkyl)C(O)H, —N(alkyl)C(O)alkyl, —N(aryl)C(O)H, —N(aryl)C(O)alkyl,—NHCO₂alkyl, —N(alkyl)CO₂alkyl, —NHC(O)NH₂, —N(alkyl)C(O)NH₂,—NHC(O)NH-alkyl, —NHC(O)N(alkyl)₂, —N(alkyl)C(O)NH-alkyl,N(alkyl)C(O)N(alkyl)₂, —NHSO₂-alkyl, —N(alkyl)SO₂-alkyl, —C(O)alkyl,—C(O)aryl, —OC(O)alkyl, —OC(O)aryl, —CO₂-alkyl, —CO₂-aryl, —CO₂H,—C(O)NH₂, —C(O)NH-alkyl, —C(O)N(alkyl)₂, —C(O)NH-aryl, —C(O)N(aryl)₂,—C(O)N(alkyl)(aryl), —S(O)alkyl, —S(O)aryl, —SO₂alkyl, —SO₂aryl,—SO₂NH₂, —SO₂NH-alkyl, and —SO₂N(alkyl)₂;R¹¹ is independently H, C₁₋₆ alkyl, C₃-C₁₀ cycloalkyl, or together withnitrogen forms a 5- or 6-membered heterocyclic ring;R¹² and R¹³ are independently H, C₁₋₆ alkyl, C₂₋₆ alkenyl, or C₂₋₆alkynyl;R¹⁴ is H, C₁₋₆ alkyl, or —CH₂-aryl;

X is O or S;

Y is H, halo, OH, OR⁴, SH, SR⁴, or a substituted or unsubstituted alkylor aryl; andZ is H, halo, OH, OR⁴, SH, or SR⁴;or a pharmaceutically acceptable salt, hydrate, metabolite orstereoisomer thereof or a pharmaceutically acceptable salt or hydrate ofsaid stereoisomer.

In another embodiment, the invention encompasses a method of treating orpreventing a hepatitis C virus infection in a patient in need thereofcomprising administering to the patient a therapeutically orprophylactically effective amount of a TLR7 ligand selected from FormulaIIa, IIb, IIc, IId, IIe, IIf, IIg, and IIh, wherein R¹ is H or asubstituted or unsubstituted alkyl, alkenyl, or alkynyl; R² is H, OH,halo, or a substituted or unsubstituted alkyl, alkenyl, or alkynyl, or—CH₂—O-(alkyl); R³ is H, OH, or SH, or a substituted or unsubstituted—O-(alkyl), —S-(alkyl), or —NH(alkyl); R⁵ is independently H,—C(O)(C₁₋₁₈alkyl), or a racemic, L-, or D-amino acid group —C(O)CHNH₂R⁹,wherein R⁹ is an unsubstituted alkyl; R⁶ is H or OR¹⁰, wherein R¹⁰ isindependently C₁₋₆ alkyl, C₃₋₇ alkenyl, C₃₋₇ alkynyl,—(CR¹²R¹³)_(t)(C₆-C₁₀ aryl), —(CR¹²R¹³)_(t)(C₄-C₁₀ heterocyclic), and—(CR¹²R¹³)_(t>0)N(R¹⁴)CO₂C₁₋₁₈ alkyl, wherein t is an integer from 0 to4 unless otherwise indicated, and wherein the alkyl, alkenyl, aryl, andheterocyclic moieties of the foregoing groups are optionally substitutedwith 1 to 3 substituents independently selected from halo, cyano, nitro,trifluoromethyl, trifluoromethoxy, C₁-C₆ alkyl, C₂-C₆ alkenyl, C₂-C₆alkynyl, hydroxy, C₁-C₆ alkoxy, —CO₂-alkyl, —CO₂-aryl, —OC(O)alkyl, and—OC(O)aryl, and wherein R¹² and R¹³ are independently H, C₁₋₆ alkyl, orC₂₋₆ alkenyl; and R¹⁴ is H, —CH₃, or —CH₂CH₃; R⁷ is independently H or asubstituted or unsubstituted —C(O)(C₁₋₁₈alkyl) or —C(O)₂(C₁₋₁₈alkyl); R⁸is H, —OH, —O-(alkyl), —OCO₂(C₁₋₁₈alkyl), or a racemic, L-, or D-aminoacid group —OC(O)CHNH₂R¹; X is O or S; Y is H, halo, OH, OR⁴, SH, orSR⁴; and Z is H, halo, OH, OR⁴, SH, or SR⁴.

In specific embodiment, the invention encompasses a method of treatingor preventing a hepatitis C virus infection in a patient in need thereofcomprising administering to the patient a therapeutically orprophylactically effective amount of a prodrug of a TLR7 ligand selectedfrom

or a pharmaceutically acceptable salt, hydrate, or stereoisomer thereofor a pharmaceutically acceptable salt or hydrate of said stereoisomer.

In another preferred embodiment of the invention, the TLR7 ligandprodrug is an amino acid ester prodrug of the TLR7 ligand. In anotherpreferred embodiment, the amino acid ester prodrug of the TLR7 ligand isa valyl ester.

In one embodiment of the invention, R⁵ is not a racemic, L-, or D-aminoacid group —C(O)CHNH₂R⁹. In another embodiment, R⁵ is not a racemic, L-,or D-amino acid group —C(O)CHNH₂R⁹ when the TLR7 ligand prodrug isselected from a compound of Formula IIh.

In another alternative embodiment, the invention encompasses a methodfor treating or preventing hepatitis C virus infection in a patient inneed thereof, comprising administering to the patient a therapeuticallyor prophylactically effective amount of a prodrug of a TLR7 ligand and apharmaceutically acceptable excipient, carrier, or vehicle.

In a separate embodiment, the invention encompasses a method fortreating or preventing hepatitis C virus infection in a patient in needthereof, comprising administering to the patient a therapeutically orprophylactically effective amount of a prodrug of a TLR7 ligand and anadditional therapeutic agent, preferably an additional antiviral orimmunomodulatory agent.

The invention also encompasses pharmaceutical compositions suitable forparenteral administration to a patient comprising a therapeutically orpharmaceutically acceptable amount a prodrug of a TLR7 ligand of theinvention in a sterile form; pharmaceutical compositions suitable forparenteral administration to a patient comprising a therapeutically orpharmaceutically acceptable amount of a prodrug of a TLR7 ligand of theinvention; pharmaceutical compositions suitable for mucosaladministration to a patient comprising a therapeutically orpharmaceutically acceptable amount of a prodrug of a TLR7 ligand of theinvention; and pharmaceutical compositions suitable for topicaladministration to a patient comprising a therapeutically orpharmaceutically acceptable amount of a prodrug of a TLR7 ligand of theinvention. Depending on the specific tissue to be treated, additionalcomponents, such as penetration enhancers, may be used prior to, inconjunction with, or subsequent to treatment with active ingredients ofthe invention. In a preferred embodiment, each of these compositions isin single unit dosage form and comprising an amount of active ingredientsufficient to treat or prevent human infection by hepatitis C virus.

In a specific embodiment, the invention encompasses a pharmaceuticalcomposition comprising a prodrug of a TLR7 ligand selected from FormulaIIa, IIb, IIc, IId, IIe, IIf, IIg, and IIh, or a pharmaceuticallyacceptable salt, hydrate or stereoisomer thereof or a pharmaceuticallyacceptable salt or hydrate of said stereoisomer.

In another embodiment of the invention, and depending on the specifictissue to be treated, additional components including, but not limitedto penetration enhancers, molecules which target the area of theinfection and molecules which reduce the in vivo toxicity of the prodrugof a TLR7 ligand may be used prior to, in conjunction with, orsubsequent to treatment with one or more prodrugs of TLR7 ligands of theinvention.

The TLR7 ligand prodrugs are useful as immune system enhancers and havecertain immune system properties including modulation, mitogenicity,augmentation, and/or potentiation or they are intermediates forcompounds that have these properties. The compounds are expected toexpress effects after administration to a mammal on at least one of thecell populations characterized as the natural killer cells, macrophages,dendritic cells, and lymphocyte cells of the immune system of a host.Because of these properties they are useful as an anti-infectiveincluding, but not limited to antiviral agents, and as antitumor agentsor as intermediates for the same. They can be used to treat an affectedhost by serving as the active ingredients of suitable pharmaceuticalcompositions.

In one aspect of the invention, TLR7 ligand prodrugs are utilized totreat the full range of viral diseases in mammals by administering tothe mammal a therapeutically effective amount of the compounds. Viraldiseases contemplated to be treated with TLR7 ligand prodrugs includeacute and chronic infections caused by both RNA and DNA viruses. Withoutlimiting in any way the range of viral infections that may be treated,TLR7 ligand prodrugs are particularly useful in the treatment ofinfections caused by adenovirus, cytomegalovirus, hepatitis A virus(HAV), hepatitis B virus (HBV), flaviviruses including Yellow Fevervirus, hepacivirus including hepatitis C virus (HCV), herpes simplextype 1 and 2, herpes zoster, human herpesvirus 6, human immunodeficiencyvirus (HIV), human papilloma virus (HPV), influenza A virus, influenza Bvirus, measles, parainfluenza virus, pestivirus, poliovirus, poxvirus(including smallpox and monkeypox virus), rhinovirus, coronovirus,respiratory syncytial virus (RSV), multiple families of viruses thatcause hemorrhagic fevers, including the Arenaviruses (LCM, Junin virus,Machupo virus, Guanarito virus, and Lassa Fever), the Bunyaviruses(Hanta viruses and Rift Valley Fever) and Filoviruses (Ebola and Marburgvirus), a range of viral encephalitides including West Nile virus,LaCrosse virus, California Encephalitis virus, Venezuelan EquineEncephalitis virus, Eastern Equine Encephalitis virus, Western EquineEncephalitis virus, Japanese Encephalitis virus, Kysanur Forest virus,and tickborne viruses such as Crimean-Congo Hemorrhagic fever virus.

In another aspect of the invention, TLR7 ligand prodrugs are utilized totreat bacterial, fungal, and protozoal infections in mammals byadministering to the mammal a therapeutically effective amount of theprodrugs. The full range of pathogenic microorganisms is contemplated tobe treatable by the TLR7 ligand prodrugs of the present invention,including without limitation those organisms that are resistant toantibiotics. The ability of TLR7 ligand prodrugs to activate multiplecomponents of the immune system bypasses resistance mechanisms commonlyfound to reduce susceptibility to antibiotics, and thus treatment ofinfections in a mammal caused by such resistant microorganisms by TLR7ligand prodrugs is a particular utility of the present invention.

In another aspect of the invention, TLR7 ligand prodrugs are utilized totreat tumors in mammals by administering to the mammal a therapeuticallyeffective amount of the prodrugs. Tumors or cancers contemplated to betreated include both those arising from aberrations in normal cellularprocesses as well as those caused by virus, and the effect may involveinhibiting the spread of cancerous cells, accelerating the killing ofcancerous cells, inhibiting transformation of virus-infected cells to aneoplastic state, inhibiting the spread of viruses from transformedcells to other normal cells, and/or arresting the growth ofvirus-transformed cells. The prodrugs of TLR7 ligands are expected to beuseful against a broad spectrum of tumors including but not limited tocarcinomas, sarcomas, and leukemias. Included in such a class aremammary, colon, bladder, lung, prostate, stomach, and pancreascarcinomas and lymphoblastic and myeloid leukemias.

In another aspect of the invention, a method of treating a mammalcomprises administering a therapeutically and/or prophylacticallyeffective amount of a pharmaceutical containing a TLR7 ligand prodrug ofthe invention. In this aspect the effect may relate to modulation ofsome portion of the mammal's immune system, especially modulation ofcytokine activities of Th1 and Th2, including but not restricted to theinterleukin family, e.g., IL-1 through IL-12, and other cytokines suchas TNF alpha, and interferons including interferon alpha, interferonbeta, and interferon gamma, and their downsteam effectors. Wheremodulation of Th1 and Th2 cytokines occurs, it is contemplated that themodulation may include stimulation of both Th1 and Th2, suppression ofboth Th1 and Th2, stimulation of either Th1 or Th2 and suppression ofthe other, or a bimodal modulation in which one effect on Th1/Th2 levels(such as generalized suppression) occurs at a high concentration, whileanother effect (such as stimulation of either Th1 or Th2 and suppressionof the other) occurs at a lower concentration.

In another aspect of this invention, pharmaceutical compositionscontaining a prodrug of a TLR7 ligand are administered intherapeutically effective doses to a mammal that is receivingimmunomodulatory drugs not included in this invention. In a preferredaspect, the doses of the immunomodulatory drug are reduced below theircustomary effective dose, to reduce adverse effects. In a secondpreferred aspect, the immunomodulatory drug is used at its customarydose, but with an improved therapeutic effect when a prodrug of a TLR7ligand is also administered.

In another aspect of the invention, pharmaceutical compositionscontaining a prodrug of a TLR7 ligand are administered in atherapeutically effective dose to a mammal that is receivinganti-infective drugs not included in this invention. In a preferredaspect of this invention, the pharmaceutical compositions containing aprodrug of a TLR7 ligand are administered in a therapeutically effectivedose with anti-infective drug(s) that act directly upon the infectiousagent to inhibit the growth of or kill the infectious agent.

4. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical depiction of plasma levels of isatoribine andinterferon alpha in mice.

FIG. 2 is a graphical depiction of Viral Load Changes in HCV infectedPatients receiving isatoribine.

5. DETAILED DESCRIPTION OF THE INVENTION 5.1 Definitions

Where the following terms are used in this specification, they are usedas defined below:

The terms “comprising” and “including” are used herein in their open,non-limiting sense.

The term “nucleoside” refers to a compound composed of any pentose ormodified pentose moiety attached to a specific position of a heterocycleor to the natural position of a purine (9-position) or pyrimidine(1-position) or to the equivalent position in an analog.

The term “purine” refers to nitrogenous bicyclic heterocycles.

The term “D-nucleosides” refers to the nucleoside compounds that have aD-ribose sugar moiety (e.g., Adenosine).

The term “L-nucleosides” refers to the nucleoside compounds that have aL-ribose sugar moiety.

The term “immunomodulator” refers to natural or synthetic productscapable of modifying the normal or aberrant immune system throughstimulation or suppression.

The term “NOAEL” is the No Observed Adverse Event Level, which is atoxicology term for the dose of drug that results in no significanttoxicity under the specified conditions of dose level, frequency,duration in a selected species.

“Ligand” means a low molecular weight molecule capable of binding to abiologic receptor. A ligand may be either an agonist or an antagonist,or may have no effect.

An “agonist” is a ligand that, upon binding, stimulates the receptor toexert a biologic response that is consistent with the normal biologicactivity of the receptor.

An “antagonist” is a ligand that, upon binding, causes the receptor tonot exert the normal biologic activity of the receptor.

The term “mammal” includes both animals and humans.

The term “preventing” refers to the ability of a compound or compositionof the invention to prevent a disease identified herein in mammalsdiagnosed as having the disease or who are at risk of developing suchdisease. The term also encompasses preventing further progression of thedisease in mammals who are already suffering from or have symptoms ofsuch disease.

The term “treating” refers to:

(i) preventing a disease, disorder, or condition from occurring in amammal that may be predisposed to the disease, disorder and/orcondition, but has not yet been diagnosed as having it;

(ii) inhibiting the disease, disorder, or condition, i.e., arresting itsdevelopment; and

(iii) relieving the disease, disorder, or condition, i.e., causingregression of the disease, disorder, and/or condition.

The terms “α” and “β” indicate the specific stereochemical configurationof a substituent at an asymmetric carbon atom in a chemical structure asdrawn.

The terms “patient” or “subject” mean an animal (e.g., cow, horse,sheep, pig, chicken, turkey, quail, cat, dog, mouse, rat, rabbit, guineapig, etc.) or a mammal, including chimeric and transgenic animals andmammals. In the treatment or prevention of HCV infection, the term“patient” or “subject” preferably means a monkey or a human, mostpreferably a human. In a specific embodiment the patient or subject isinfected by or exposed to the hepatitis C virus. In certain embodiments,the patient is a human infant (age 0-2), child (age 2-17), adolescent(age 12-17), adult (age 18 and up) or geriatric (age 70 and up) patient.In addition, the patient includes immunocompromised patients such as HIVpositive patients, cancer patients, patients undergoing immunotherapy orchemotherapy. In a particular embodiment, the patient is a healthyindividual, i.e., not displaying symptoms of other viral infections.

The term a “therapeutically effective amount” refers to an amount of theTLR7 ligand or prodrug of a TLR7 ligand of the invention sufficient toprovide a benefit in the treatment or prevention of viral disease, todelay or minimize symptoms associated with viral infection orviral-induced disease, or to cure or ameliorate the disease or infectionor cause thereof. In particular, a therapeutically effective amountmeans an amount sufficient to provide a therapeutic benefit in vivo.Used in connection with an amount of a compound of the invention, theterm preferably encompasses a non-toxic amount that improves overalltherapy, reduces or avoids symptoms or causes of disease, or enhancesthe therapeutic efficacy of or synergies with another therapeutic agent.

The term a “prophylactically effective amount” refers to an amount of acompound of the invention or other active ingredient sufficient toresult in the prevention of infection, recurrence or spread of viralinfection. A prophylactically effective amount may refer to an amountsufficient to prevent initial infection or the recurrence or spread ofthe infection or a disease associated with the infection. Used inconnection with an amount of a compound of the invention, the termpreferably encompasses a non-toxic amount that improves overallprophylaxis or enhances the prophylactic efficacy of or synergizes withanother prophylactic or therapeutic agent.

The term “in combination” refers to the use of more than oneprophylactic and/or therapeutic agents simultaneously or sequentiallyand in a manner that their respective effects are additive orsynergistic.

The term “pharmaceutically acceptable salts” refer to salts preparedfrom pharmaceutically acceptable non-toxic acids or bases includinginorganic acids and bases and organic acids and bases. If the inventiveTLR7 ligand prodrug is a base, the desired pharmaceutically acceptablesalt may be prepared by any suitable method available in the art, forexample, treatment of the free base with an inorganic acid, such ashydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid,phosphoric acid and the like, or with an organic acid, such as aceticacid, maleic acid, succinic acid, mandelic acid, fumaric acid, malonicacid, pyruvic acid, oxalic acid, glycolic acid, salicylic acid, apyranosidyl acid, such as glucuronic acid or galacturonic acid, analpha-hydroxy acid, such as citric acid or tartaric acid, an amino acid,such as aspartic acid or glutamic acid, an aromatic acid, such asbenzoic acid or cinnamic acid, a sulfonic acid, such asp-toluenesulfonic acid or ethanesulfonic acid, or the like. If theinventive TLR7 ligand prodrug is an acid, the desired pharmaceuticallyacceptable salt may be prepared by any suitable method, for example,treatment of the free acid with an inorganic or organic base, such as anamine (primary, secondary or tertiary), an alkali metal hydroxide oralkaline earth metal hydroxide, or the like. Illustrative examples ofsuitable salts include organic salts derived from amino acids, such asglycine and arginine, ammonia, primary, secondary, and tertiary amines,and cyclic amines, such as piperidine, morpholine and piperazine, andinorganic salts derived from sodium, calcium, potassium, magnesium,manganese, iron, copper, zinc, aluminum and lithium.

The term “prodrug” is intended to mean any chemical entity that afteradministration is converted via metabolic actions or solvolysis to adifferent chemical entity that retains biological activity.

The term “TLR7 ligand prodrug” is intended to mean any chemical entitythat after administration is converted via metabolic actions orsolvolysis to a different chemical entity that retains biologicalactivity and that is a ligand for TLR7. A TLR7 ligand prodrug may itselfbe a ligand for TLR7, or it may be “masked” in that it does not functionefficiently as a TLR7 ligand.

The term “masked TLR7 ligand prodrug” is intended to mean any chemicalentity that after administration is converted via metabolic actions orsolvolysis to a different chemical entity that retains biologicalactivity and that is a ligand for TLR7, and where the administeredchemical entity is a less efficient ligand for TLR7 than the chemicalentity arising from metabolic conversion or solvolysis.

The term “a pharmaceutically active metabolite” is intended to mean apharmacologically active product produced through metabolism in the bodyof a specified compound or salt thereof. After entry into the body, mostdrugs are substrates for chemical reactions that may change theirphysical properties and biologic effects. These metabolic conversions,which usually affect the polarity of the TLR7 ligand, alter the way inwhich drugs are distributed in and excreted from the body. However, insome cases, metabolism of a drug is required for therapeutic effect. Forexample, many anticancer drugs of the anti-metabolite class must beconverted to their active forms after they have been transported into acancer cell.

As used herein, unless otherwise specified, the term “alkyl” means asaturated straight chain or branched non-cyclic hydrocarbon having from1 to 20 carbon atoms, preferably 1-10 carbon atoms and most preferably1-4 carbon atoms. Representative saturated straight chain alkyls include-methyl, -ethyl, -n-propyl, -n-butyl, -n-pentyl, -n-hexyl, -n-heptyl,-n-octyl, -n-nonyl and -n-decyl; while saturated branched alkyls include-isopropyl, -sec-butyl, -isobutyl, -tert-butyl, -isopentyl,2-methylbutyl, 3-methylbutyl, 2-methylpentyl, 3-methylpentyl,4-methylpentyl, 2-methylhexyl, 3-methylhexyl, 4-methylhexyl,5-methylhexyl, 2,3-dimethylbutyl, 2,3-dimethylpentyl,2,4-dimethylpentyl, 2,3-dimethylhexyl, 2,4-dimethylhexyl,2,5-dimethylhexyl, 2,2-dimethylpentyl, 2,2-dimethylhexyl,3,3-dimtheylpentyl, 3,3-dimethylhexyl, 4,4-dimethylhexyl, 2-ethylpentyl,3-ethylpentyl, 2-ethylhexyl, 3-ethylhexyl, 4-ethylhexyl,2-methyl-2-ethylpentyl, 2-methyl-3-ethylpentyl, 2-methyl-4-ethylpentyl,2-methyl-2-ethylhexyl, 2-methyl-3-ethylhexyl, 2-methyl-4-ethylhexyl,2,2-diethylpentyl, 3,3-diethylhexyl, 2,2-diethylhexyl, 3,3-diethylhexyland the like. An alkyl group can be unsubstituted or substituted.

As used herein, unless otherwise specified the term “aryl” means acarbocyclic aromatic ring containing from 5 to 14 ring atoms. The ringatoms of a carbocyclic aryl group are all carbon atoms. Aryl ringstructures include compounds having one or more ring structures such asmono-, bi-, or tricyclic compounds as well as benzo-fused carbocyclicmoieties such as 5,6,7,8-tetrahydronaphthyl and the like. Preferably,the aryl group is a monocyclic ring or bicyclic ring. Representativearyl groups include phenyl, tolyl, anthracenyl, fluorenyl, indenyl,azulenyl, phenanthrenyl and naphthyl. A carbocyclic aryl group can beunsubstituted or substituted.

The term “substituted” means that the specified group or moiety bearsone or more substituents. The term “unsubstituted” means that thespecified group bears no substituents. A “substituted alkyl” or“substituted aryl” is substituted by one or more substituents includinghalogen (F, Cl, Br, or I), lower alkyl(C₁₋₆), —OH, —NO₂, —CN, —CO₂H,—O-lower alkyl, -aryl, -aryl-lower alkyl, —CO₂CH₃, —CONH₂, —OCH₂CONH₂,—NH₂, —SO₂NH₂, haloalkyl (e.g., —CF₃, —CH₂CF₃), —O-haloalkyl (e.g.,—OCF₃, —OCHF₂), and the like.

As used herein and unless otherwise indicated, the term “optically pure”or “stereomerically pure” means a composition that comprises onestereoisomer of a compound and is substantially free of otherstereoisomers of that compound. For example, a stereomerically purecompound having one chiral center will be substantially free of theopposite enantiomer of the compound. A typical stereomerically purecompound comprises greater than about 80% by weight of one stereoisomerof the compound and less than about 20% by weight of other stereoisomersof the compound, more preferably greater than about 90% by weight of onestereoisomer of the compound and less than about 10% by weight of theother stereoisomers of the compound, even more preferably greater thanabout 95% by weight of one stereoisomer of the compound and less thanabout 5% by weight of the other stereoisomers of the compound, and mostpreferably greater than about 97% by weight of one stereoisomer of thecompound and less than about 3% by weight of the other stereoisomers ofthe compound. Since many of the compounds of the invention comprisesaccharides which can exist in either the D or L forms, the inventionencompasses either or both D and L sugars. As such, for example, astereomerically pure D sugar will be substantially free of the L form.In an alternative embodiment, the use of L forms of a TLR7 ligand willbe substantially free of the D form. Thus, the methods and compositionsdisclosed herein include in an alternative embodiment the use of suchlevorotatory sugars or polymers made therefrom.

The compounds of the invention may exhibit the phenomenon oftautomerism. While Formulas I and II cannot expressly depict allpossible tautomeric forms, it is to be understood that Formula I isintended to represent any tautomeric form of the depicted compound andare not to be limited merely to a specific compound form depicted by theformula drawings. For example, it is understood that regardless ofwhether or not the substituents are shown in their enol or their ketoform, they represent the same compound (as shown in the Formula IIaexample below).

5.2 Identification of TLR7 Ligands

Known TLR7 ligands include, but are not limited to (1) guanosineanalogs, such as 7-deazaguanosine and related compounds, including butnot limited to those described in Townsend, J. Heterocyclic Chem, 13,1363 (1976), and Seela, et al, Chem. Ber., 114(10), 3395-3402 (1981);7-allyl, 8-oxo-guanosine (loxorabine) and related compounds, includingbut not limited to those described in Reitz, et al., J. Med. Chem., 37,3561-3578 (1994); 7-methyl, 9-deazaguanosine and related compoundsincluding, but not limited to, those described in Girgis et al., J. Med.Chem., 33, 2750-2755 (1990); 8-bromoguanosine and other 8-halogensubstituted purines compounds including, but not limited to, thosedescribed in U.S. Pat. No. 4,643,992;6-amino-9-benzyl-2-butoxy-9H-purin-8-ol, and other 2, 6, 8,9-substituted purines including, but not limited to, those described inHirota et al., J. Med. Chem., 45, 5419-5422 (2002), Henry et al., J.Med. Chem., 33, 2127-2130 (1990), Michael et al., J. Med. Chem., 36,3431-3436 (1993), Furneaux et al., J. Org. Chem., 64 (22), 8411-8412(1999), Barrio et al; J. Org. Chem., 61, 6084-6085 (1996), U.S. Pat. No.4,539,205, U.S. Pat. No. 5,011,828, U.S. Pat. No. 5,041,426, U.S. Pat.No. 4,880,784, and International Patent Application Publication Nos. WO94/07904; (2) imidazoquinolines, including but not limited to1-(4-amino-2-ethoxymethyl-imidazo[4,5-c]quinolin-1-yl)-2-methyl-propan-2-ol(imiquimoid), as described in International Patent ApplicationPublication No. WO 94/17043;1-isobutyl-1H-imidazo[4,5-c]quinolin-4-ylamine (resiquimoid) asdescribed in International Patent Application Publication No. WO94/17043 and U.S. patent application Ser. Nos. 10/357,777 (United StatesPatent Application Publication No. US 2003/0195209), 10/357,733 (UnitedStates Patent Application Publication No. US 2003/0186949), 10/358,017(United States Patent Application Publication No. US 2003/0176458),10/357,995 (United States Patent Application Publication No. US2003/0162806), 10/165,222 (United States Patent Application PublicationNo. US 2003/0100764), 10/011,921 (United States Patent ApplicationPublication No. US 2003/0065005) and 10/013,059 (United States PatentApplication Publication No. US 2002/0173655); U.S. Pat. No. 5,395,937;International Patent Application Publication No. WO 98/17279; and (3)pyrimidine derivatives, including but not limited to2-amino-6-bromo-5-phenyl-3H-pyrimidin-4-one (bropirimine), and similarsubstituted pyrimidines including, but not limited to, those describedin Wierenga et al., J. Med. Chem, 23, 239-240 (1980), Fan et al., J.Heterocyclic Chem., 30, 1273 (1993), Skilnick et al., J. Med. Chem., 29,1499-1504 (1986), Fried, et al., J. Med. Chem., 23, 237-239 (1980), andFujiwara et al., Bioorg. Med. Chem. Lett., 10(12) 1317-1320 (2000). Theentireties of each of the patents, patent publications and publicationsidentified herein are incorporated herein by reference.

In addition to the above TLR7 ligands, additional TLR7 ligands can bereadily identified by known screening methods. See, e.g., Hirota et al.,J. Med. Chem., 45, 5419-5422 (2002); and Akira S. et al., ImmunologyLetters, 85, 85-95 (2003). Using a variant of one of these knownscreening methods (as described in Section 6.1), analogs and derivativesof adenine were also identified as TLR7 ligands. Adenine derivativesknown in the art are described in European Patent ApplicationPublication Nos. EP 1 035 123, EP 1 043 021, and EP 0 882 727; U.S. Pat.No. 6,376,501; U.S. Pat. No. 6,329,381; U.S. Pat. No. 6,028,076, andUnited States Patent Application Publication No. US 2003/0162806.

The TLR7 ligands of Formulas Ia-Ih can be synthesized using methodsknown to one of skill in the art, particularly in light of thereferences and patents listed above.

5.3 Preparation of TLR7 Ligand Prodrugs

The TLR7 ligand prodrugs of the invention are prepared by making an (a)amide, carbamate, or amidine moiety after conversion of a TLR7 ligandamine substituent, (b) ester, carbonate, carbamate, ether, imidate,acetal, or ketal moiety after conversion of a TLR7 ligand alcoholsubstituent, (c) acetal or ketal moiety after conversion of a TLR7ligand amine substituent, (d) imidate moiety after conversion of a TLR7ligand carbonyl of an amido substituent, (e) deoxygenated moiety afterconversion of a TLR7 ligand oxo substituent of pyrimidine or guanosine,or (f) amine. For example, TLR7 ligand prodrugs are prepared by either(1) converting an hydroxyl (OH) substituents of the TLR7 ligand into anamino acid ester, or (2) making an amine substituent of the TLR7 ligandinto an amide or carbamate. The process for preparing prodrugs is wellknown in the art and is described by Burger's Medicinal Chemistry andDrug Chemistry, 1, 172-178, 949-982 (1995). See also Bertolini et al.,J. Med. Chem., 40, 2011-2016 (1997); Shan, et al., J. Pharm. Sci., 86(7), 765-767; Bagshawe, Drug Dev. Res., 34, 220-230 (1995); Bodor,Advances in Drug Res., 13, 224-331 (1984); Bundgaard, Design of Prodrugs(Elsevier Press 1985); Larsen, Design and Application of Prodrugs, DrugDesign and Development (Krogsgaard-Larsen et al., eds., Harwood AcademicPublishers, 1991); Dear et al., J. Chromatogr. B, 748, 281-293 (2000);Spraul et al., J Pharmaceutical &Biomedical Analysis, 10, 601-605(1992); and Prox et al., Xenobiol., 3, 103-112 (1992).

Schemes 1-18 show a general procedure to prepare representativecompounds of Formula II.

Schemes 1-6 describe how 5′-amino acid esters can be synthesized fromanalogs and derivatives of guanosine.

In a typical synthetic route, the 2′,3′-hydroxyl groups of theβ-D-ribose moiety of Formula Ia, Ib, Id, Ie, or Ih can first protected,preferably with an acetonide as shown for 2, 6, 10, or 14. The free5′-hydroxyl can then be subjected to a variety of esterification methodswith a N-protected amino acid to form 3, 7, 11, or 15. The nitrogen ofthe amino acid ester and the 2′,3′-hydroxyls of the ribose unit can thenbe subjected to various deprotection conditions, preferablyconcurrently, followed by salt formation of the free amine of the aminoacid ester as illustrated for 4, 8, 12, or 16.

In the synthetic routes shown in Schemes 5 and 6, the 2′,3′-hydroxylgroups of the β-D-ribose moiety of compound 17 and 21 were firstprotected with an acetonide to form 18 and 22 respectively. The free5′-hydroxyl was then subjected to esterification with aN-tert-butoxycarbonyl valine to form 19 and 23 respectively. Thenitrogen of the amino acid ester and the 2′,3′-hydroxyls of the ribosewere concurrently deprotected forming the hydrochloride salts asillustrated for 20 and 24.

Schemes 7 and 8 describe how carbamates and carbonates can besynthesized from analogs and derivatives of adenine.

In a typical synthetic route, the amino group of Formula If can besubjected to a variety of conditions with carbonates or chloroformatesto form carbamates. In the case of 27, the N-terminal protected amine ofthe resulting amino acid ester can be subjected to deprotectionconditions to form salts such as 28.

In Scheme 8 the hydroxyl group of adenine derivative 29 was esterifiedwith n-hexyl chloroformate to give carbonate 30.

Schemes 9 and 10 describes how carbamates and can be synthesized fromimidazoquinoline analogs.

In a typical synthetic route, the amino group of analogs of Formula Iccan be subjected to a variety of conditions with carbonates,pyrocarbonates or chloroformates to form carbamates.

In Scheme 10 imidazoquinoline 31 was treated with n-pentyl pyrocarbonateto give pentyl carbamate 34.

Schemes 11-12 described how to synthesize carbamates and imidates ofpyrimidines of formula Ig.

In a typical synthesis of carbamates, the amino group of 35 wassubjected to ethyl pyrocarbonate under conditions shown above to formcarbamate 36.

In a typical synthesis of imidates, the amino group of 35 was subjectedto ethyl alcohol under Mitsunobu type conditions shown above to formethoxy derivative 37.

Scheme 13 describes how carbamates and can be synthesized fromimidazoquinoline analogs.

In a typical synthetic route, the amino group of a derivative of FormulaIc can be subjected to a variety of conditions with carbonates,pyrocarbonates or chloroformates to form carbamates.

Scheme 14 shows a general procedure for preparing7-allyl-2-Amino-9-β-D-ribofuranosyl-7,9-dihydro-purin-8-one.

In a typical synthetic routes,7-allyl-2-amino-9-β-D-ribofuranosyl-7,9-dihydro-1H-purine-6,8-dione 17,was protected at the 2′,3′,5′-hydroxyl groups of the β-D-ribose,preferably with acyl groups as shown for 40, can be subjected to avariety of conditions to convert the carbonyl at the C-6 position tovarious groups, including but not limited to halogen, as shown for 41,that are susceptible to reduction. Following reduction under hetero- orhomogeneous reaction conditions, the 2′,3′,5′-hydroxyls of the riboseunit are then subjected to appropriate deprotection conditions, toproduce 43. Compound 43 can further be appropriately modified if sodesired.

Scheme 15 shows a general procedure for preparing7-allyl-2-Amino-6-ethoxy-9-β-D-ribofuranosyl-7,9-dihydro-purin-8-one.

In a typical synthetic route, 40 can be subjected to a variety ofconditions to convert the carbonyl at the C-6 position to variousimido-ethers, including but not limited to ethyl, as shown for 44. The2′,3′,5′-hydroxyls of the ribose unit are then subjected to appropriatedeprotection conditions, to produce 45. Compound 45 can further beappropriately modified if so desired.

Scheme 16 describes how ethers can be synthesized from analogs andderivatives of adenine.

In a typical synthetic route, the adenine derivative can be halogenatedat C-8. The halogen can then be displaced with an appropriate alkoxideto form derivatives such as 64.

Scheme 17 shows a general procedure for preparing7-allyl-2-Amino-6-substitutedalkoxy-9-β-D-ribofuranosyl-7,9-dihydro-purin-8-ones.

In a typical synthetic route, the hydroxyl groups on ribose of 17 can beprotected as silyl ethers. The carbonyl at the C-6 position of 69 can besubjected to a variety of conditions to convert the carbonyl to variousimido-ethers, including but not limited to the ether of4-hydroxymethyl-5-methyl-[1,3]dioxol-2-one, as shown for 70. The2′,3′,5′-hydroxyls of the ribose unit are then subjected to appropriatedeprotection conditions, to produce 71.

Scheme 18 shows a general procedure for preparing7-allyl-2-Amino-6-substitutedalkoxy-9-β-D-ribofuranosyl-7,9-dihydro-purin-8-ones.

The carbonyl at the C-6 position of 69 can be subjected to a variety ofconditions to convert the carbonyl to various imido-ethers, includingbut not limited to the ether of N-methyl-N-(hydroxymethyl)urethane, asshown for 72. The 2′,3′,5′-hydroxyls of the ribose unit are thensubjected to appropriate deprotection conditions, to produce 73.Compound 73 can further be appropriately modified if so desired.

5.4 Methods of Treatment and Prevention of Hepatitis C Viral Infections

The present invention provides methods for treating or preventing ahepatitis C virus infection in a patient in need thereof.

The present invention further provides methods for introducing atherapeutically effective amount of a TLR7 ligand or a prodrug thereof,or combination of such ligands and prodrugs into the blood stream of apatient in the treatment and/or prevention of hepatitis C viralinfections.

The magnitude of a prophylactic or therapeutic dose of a TLR7 ligand orTLR7 ligand prodrug of the invention or a pharmaceutically acceptablesalt, solvate, hydrate, or stereoisomer thereof in the acute or chronictreatment or prevention of an infection will vary, however, with thenature and severity of the infection, and the route by which the activeingredient is administered. The dose, and in some cases the dosefrequency, will also vary according to the infection to be treated, theage, body weight, and response of the individual patient. Suitabledosing regimens can be readily selected by those skilled in the art withdue consideration of such factors.

The methods of the present invention are particularly well suited forhuman patients. In particular, the methods and doses of the presentinvention can be useful for immunocompromised patients including, butnot limited to cancer patients, HIV infected patients, and patients withan immunodegenerative disease. Furthermore, the methods can be usefulfor immunocompromised patients currently in a state of remission. Themethods and doses of the present invention are also useful for patientsundergoing other antiviral treatments. The prevention methods of thepresent invention are particularly useful for patients at risk of viralinfection. These patients include, but are not limited to health careworkers, e.g., doctors, nurses, hospice care givers; military personnel;teachers; childcare workers; patients traveling to, or living in,foreign locales, in particular third world locales including social aidworkers, missionaries, and foreign diplomats. Finally, the methods andcompositions include the treatment of refractory patients or patientsresistant to treatment such as resistance to viral polymeraseinhibitors, protease inhibitors, etc.

Doses

Toxicity and efficacy of the compounds of the invention can bedetermined by standard pharmaceutical procedures in cell cultures orexperimental animals, e.g., for determining the LD₅₀ (the dose lethal to50% of the population) and the ED₅₀ (the dose therapeutically effectivein 50% of the population). The dose ratio between toxic and therapeuticeffects is the therapeutic index and it can be expressed as the ratioLD₅₀/ED₅₀.

The data obtained from the cell culture assays and animal studies can beused in formulating a range of dosage of the compounds for use inhumans. The dosage of such compounds lie preferably within a range ofcirculating concentrations that include the ED₅₀ with little or notoxicity. The dosage may vary within this range depending upon thedosage form employed and the route of administration utilized. For anycompound used in the method of the invention, the therapeuticallyeffective dose can be estimated initially from cell culture assays. Adose may be formulated in animal models to achieve a circulating plasmaconcentration range that includes the IC₅₀ (i.e., the concentration ofthe test compound that achieves a half-maximal inhibition of symptoms)as determined in cell culture; alternatively, the dose of the TLR7ligand prodrug may be formulated in animal models to achieve acirculating plasma concentration range of the TLR7 ligand thatcorresponds to the concentration required to achieve a fixed magnitudeof response. Such information can be used to more accurately determineuseful doses in humans. Levels in plasma may be measured, for example,by high performance liquid chromatography.

The protocols and compositions of the invention are preferably tested invitro, and then in vivo, for the desired therapeutic or prophylacticactivity, prior to use in humans. For example, in vitro assays which canbe used to determine whether administration of a specific therapeuticprotocol is indicated, include in vitro cell culture assays in whichcells that are responsive to the effects of the TLR7 ligands are exposedto the ligand and the magnitude of response is measured by anappropriate technique. The assessment of the TLR7 ligand potency is thenevaluated with respect to the TLR7 ligand prodrug potency, and thedegree of conversion of the TLR7 ligand prodrug. Compounds for use inmethods of the invention can be tested in suitable animal model systemsprior to testing in humans, including but not limited to in rats, mice,chicken, cows, monkeys, rabbits, hamsters, etc. The compounds can thenbe used in the appropriate clinical trials.

The magnitude of a prophylactic or therapeutic dose of a prodrug of aTLR7 ligand of the invention or a pharmaceutically acceptable salt,solvate, hydrate, or stereoisomer thereof in the acute or chronictreatment or prevention of an infection or condition will vary with thenature and severity of the infection, and the route by which the activeingredient is administered. The dose, and perhaps the dose frequency,will also vary according to the infection to be treated, the age, bodyweight, and response of the individual patient. Suitable dosing regimenscan be readily selected by those skilled in the art with dueconsideration of such factors. In one embodiment, the dose administereddepends upon the specific compound to be used, and the weight andcondition of the patient. Also, the dose may differ for variousparticular TLR7 ligands prodrugs; suitable doses can be predicted on thebasis of the aforementioned in vitro measurements, in particular by useof such measurements of the TLR7 ligand to which the TLR7 ligand prodrugis related, and on the basis of animal studies, such that smaller doseswill be suitable for those TLR7 ligand prodrugs that show effectivenessat lower concentrations than other TLR7 ligand prodrugs when measured inthe systems described or referenced herein. In general, the dose per dayis in the range of from about 0.001 to 100 mg/kg, preferably about 1 to25 mg/kg, more preferably about 5 to 15 mg/kg. For treatment of humansinfected by hepatitis C viruses, about 0.1 mg to about 15 g per day isadministered in about one to four divisions a day, preferably 100 mg to12 g per day, more preferably from 100 mg to 8000 mg per day. In apreferred embodiment for compounds such as prodrugs of3-β-D-ribofuranosylthiazolo[4,5-d]pyrimidines from 200 mg to 8000 mg perday is administered in about one to four divisions a day. Additionally,the recommended daily dose ran can be administered in cycles as singleagents or in combination with other therapeutic agents. In oneembodiment, the daily dose is administered in a single dose or inequally divided doses. In a related embodiment, the recommended dailydose can be administered once time per week, two times per week, threetimes per week, four times per week or five times per week.

In a preferred embodiment, the compounds of the invention areadministered to provide systemic distribution of the compound within thepatient. In a related embodiment, the compounds of the invention areadministered to produce a systemic effect in the body.

In another embodiment the compounds of the invention are administeredvia oral, mucosal (including sublingual, buccal, rectal, nasal, orvaginal), parenteral (including subcutaneous, intramuscular, bolusinjection, intraarterial, or intravenous), transdermal, or topicaladministration. In a specific embodiment the compounds of the inventionare administered via mucosal (including sublingual, buccal, rectal,nasal, or vaginal), parenteral (including subcutaneous, intramuscular,bolus injection, intraarterial, or intravenous), transdermal, or topicaladministration. In a further specific embodiment, the compounds of theinvention are administered via oral administration. In a furtherspecific embodiment, the compounds of the invention are not administeredvia oral administration.

Different therapeutically effective amounts may be applicable fordifferent infections, as will be readily known by those of ordinaryskill in the art. Similarly, amounts sufficient to treat or prevent suchinfections, but insufficient to cause, or sufficient to reduce, adverseeffects associated with conventional therapies are also encompassed bythe above described dosage amounts and dose frequency schedules.

Combination Therapy

Specific methods of the invention further comprise the administration ofan additional therapeutic agent (i.e., a therapeutic agent other than acompound of the invention). In certain embodiments of the presentinvention, the compounds of the invention can be used in combinationwith at least one other therapeutic agent. Therapeutic agents include,but are not limited to antibiotics, antiemetic agents, antidepressants,and antifungal agents, anti-inflammatory agents, antiviral agents,anticancer agents, immunomodulatory agents, β-interferons, alkylatingagents, hormones or cytokines. In a preferred embodiment the inventionencompasses the administration of an additional therapeutic agent thatis HCV specific or demonstrates anti-HCV activity.

The TLR7 ligands prodrugs of the invention can be administered orformulated in combination with antibiotics. For example, they can beformulated with a macrolide (e.g., tobramycin (Tobi®)), a cephalosporin(e.g., cephalexin (Keflex®), cephradine (Velosef®), cefuroxime(Ceftin®), cefprozil (Cefzil®), cefaclor (Ceclor®), cefixime (Suprax®)or cefadroxil (Duricef®)), a clarithromycin (e.g., clarithromycin(Biaxin®)), an erythromycin (e.g., erythromycin (EMycin®)), a penicillin(e.g., penicillin V (V-Cillin K® or Pen Vee K®)) or a quinolone (e.g.,ofloxacin (Floxin®), ciprofloxacin (Cipro®) or norfloxacin (Noroxin®)),aminoglycoside antibiotics (e.g., apramycin, arbekacin, bambermycins,butirosin, dibekacin, neomycin, neomycin, undecylenate, netilmicin,paromomycin, ribostamycin, sisomicin, and spectinomycin), amphenicolantibiotics (e.g., azidamfenicol, chloramphenicol, florfenicol, andthiamphenicol), ansamycin antibiotics (e.g., rifamide and rifampin),carbacephems (e.g., loracarbef), carbapenems (e.g., biapenem andimipenem), cephalosporins (e.g., cefaclor, cefadroxil, cefamandole,cefatrizine, cefazedone, cefozopran, cefpimizole, cefpiramide, andcefpirome), cephamycins (e.g., cefbuperazone, cefmetazole, andcefminox), monobactams (e.g., aztreonam, carumonam, and tigemonam),oxacephems (e.g. flomoxef, and moxalactam), penicillins (e.g.,amdinocillin, amdinocillin pivoxil, amoxicillin, bacampicillin,benzylpenicillinic acid, benzylpenicillin sodium, epicillin,fenbenicillin, floxacillin, penamccillin, penethamate hydriodide,penicillin o-benethamine, penicillin 0, penicillin V, penicillin Vbenzathine, penicillin V hydrabamine, penimepicycline, andphencihicillin potassium), lincosamides (e.g., clindamycin, andlincomycin), amphomycin, bacitracin, capreomycin, colistin, enduracidin,enviomycin, tetracyclines (e.g., apicycline, chlortetracycline,clomocycline, and demeclocycline), 2,4-diaminopyrimidines (e.g.,brodimoprim), nitrofurans (e.g. furaltadone, and furazolium chloride),quinolones and analogs thereof (e.g. cinoxacin, clinafloxacin,flumequine, and grepagloxacin), sulfonamides (e.g., acetylsulfamethoxypyrazine, benzylsulfamide, noprylsulfamide,phthalylsulfacetamide, sulfachrysoidine, and sulfacytine), sulfones(e.g., diathymosulfone, glucosulfone sodium, and solasulfone),cycloserine, mupirocin and tuberin.

The TLR7 ligand prodrugs of the invention can also be administered orformulated in combination with an antiemetic agent. Suitable antiemeticagents include, but are not limited to, metoclopromide, domperidone,prochlorperazine, promethazine, chlorpromazine, trimethobenzamide,ondansetron, granisetron, hydroxyzine, acethylleucine monoethanolamine,alizapride, azasetron, benzquinamide, bietanautine, bromopride,buclizine, clebopride, cyclizine, dimenhydrinate, diphenidol,dolasetron, meclizine, methallatal, metopimazine, nabilone, oxyperndyl,pipamazine, scopolamine, sulpiride, tetrahydrocannabinols,thiethylperazine, thioproperazine, tropisetron, and mixtures thereof.

The TLR7 ligand prodrugs of the invention can be administered orformulated in combination with an antidepressant. Suitableantidepressants include, but are not limited to, binedaline, caroxazone,citalopram, dimethazan, fencamine, indalpine, indeloxazinehydrocholoride, nefopam, nomifensine, oxitriptan, oxypertine,paroxetine, sertraline, thiazesim, trazodone, benmoxine, iproclozide,iproniazid, isocarboxazid, nialamide, octamoxin, phenelzine, cotinine,rolicyprine, rolipram, maprotiline, metralindole, mianserin,mirtazepine, adinazolam, amitriptyline, amitriptylinoxide, amoxapine,butriptyline, clomipramine, demexiptiline, desipramine, dibenzepin,dimetacrine, dothiepin, doxepin, fluacizine, imipramine, imipramineN-oxide, iprindole, lofepramine, melitracen, metapramine, nortriptyline,noxiptilin, opipramol, pizotyline, propizepine, protriptyline,quinupramine, tianeptine, trimipramine, adrafinil, benactyzine,bupropion, butacetin, dioxadrol, duloxetine, etoperidone, febarbamate,femoxetine, fenpentadiol, fluoxetine, fluvoxamine, hematoporphyrin,hypericin, levophacetoperane, medifoxamine, milnacipran, minaprine,moclobemide, nefazodone, oxaflozane, piberaline, prolintane,pyrisuccideanol, ritanserin, roxindole, rubidium chloride, sulpiride,tandospirone, thozalinone, tofenacin, toloxatone, tranylcypromine,L-tryptophan, venlafaxine, viloxazine, and zimeldine.

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with an antifungal agent.Suitable antifungal agents include but are not limited to amphotericinB, itraconazole, ketoconazole, fluconazole, intrathecal, flucytosine,miconazole, butoconazole, clotrimazole, nystatin, terconazole,tioconazole, ciclopirox, econazole, haloprogrin, naftifine, terbinafine,undecylenate, and griseofuldin.

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with an anti-inflammatoryagent. Useful anti-inflammatory agents include, but are not limited to,non-steroidal anti-inflammatory drugs such as salicylic acid,acetylsalicylic acid, methyl salicylate, diflunisal, salsalate,olsalazine, sulfasalazine, acetaminophen, indomethacin, sulindac,etodolac, mefenamic acid, meclofenamate sodium, tolmetin, ketorolac,dichlofenac, ibuprofen, naproxen, naproxen sodium, fenoprofen,ketoprofen, flurbinprofen, oxaprozin, piroxicam, meloxicam, ampiroxicam,droxicam, pivoxicam, tenoxicam, nabumetome, phenylbutazone,oxyphenbutazone, antipyrine, aminopyrine, apazone and nimesulide;leukotriene antagonists including, but not limited to, zileuton,aurothioglucose, gold sodium thiomalate and auranofin; steroidsincluding, but not limited to, alclometasone diproprionate, amcinonide,beclomethasone dipropionate, betametasone, betamethasone benzoate,betamethasone diproprionate, betamethasone sodium phosphate,betamethasone valerate, clobetasol proprionate, clocortolone pivalate,hydrocortisone, hydrocortisone derivatives, desonide, desoximatasone,dexamethasone, flunisolide, flucoxinolide, flurandrenolide, halcinocide,medrysone, methylprednisolone, methprednisolone acetate,methylprednisolone sodium succinate, mometasone furoate, paramethasoneacetate, prednisolone, prednisolone acetate, prednisolone sodiumphosphate, prednisolone tebuatate, prednisone, triamcinolone,triamcinolone acetonide, triamcinolone diacetate, and triamcinolonehexacetonide; and other anti-inflammatory agents including, but notlimited to, methotrexate, colchicine, allopurinol, probenecid,sulfinpyrazone and benzbromarone.

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with another antiviral agent.Useful antiviral agents include, but are not limited to, proteaseinhibitors, nucleoside reverse transcriptase inhibitors, non-nucleosidereverse transcriptase inhibitors and nucleoside analogs. The antiviralagents include but are not limited to zidovudine, acyclovir,gangcyclovir, vidarabine, idoxuridine, trifluridine, levovirin,viramidine and ribavirin, as well as foscarnet, amantadine, rimantadine,saquinavir, indinavir, amprenavir, lopinavir, ritonavir, thealpha-interferons, beta-interferons, gamma-interferons, adefovir,clevudine, entecavir, and pleconaril.

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with an immunomodulatoryagent. Immunomodulatory agents include, but are not limited to,methothrexate, leflunomide, cyclophosphamide, cyclosporine A,mycophenolate mofetil, rapamycin (sirolimus), mizoribine,deoxyspergualin, brequinar, malononitriloamindes (e.g., leflunamide), Tcell receptor modulators, and cytokine receptor modulators, peptidemimetics, and antibodies (e.g., human, humanized, chimeric, monoclonal,polyclonal, Fvs, ScFvs, Fab or F(ab)2 fragments or epitope bindingfragments), nucleic acid molecules (e.g., antisense nucleic acidmolecules and triple helices), small molecules, organic compounds, andinorganic compounds. Examples of T cell receptor modulators include, butare not limited to, anti-T cell receptor antibodies (e.g., anti-CD4antibodies (e.g., cM-T412 (Boeringer), IDEC-CE9.1® (IDEC and SKB), mAB4162W94, Orthoclone and OKTcdr4a (Janssen-Cilag)), anti-CD3 antibodies(e.g., Nuvion (Product Design Labs), OKT3 (Johnson & Johnson), orRituxan (IDEC)), anti-CD5 antibodies (e.g., an anti-CD5 ricin-linkedimmunoconjugate), anti-CD7 antibodies (e.g., CHH-380 (Novartis)),anti-CD8 antibodies, anti-CD40 ligand monoclonal antibodies (e.g.,IDEC-131 (IDEC)), anti-CD52 antibodies (e.g., CAMPATH 1H (Ilex)),anti-CD2 antibodies, anti-CD11a antibodies (e.g., Xanelim (Genentech)),and anti-B7 antibodies (e.g., IDEC-114 (IDEC)) and CTLA4-immunoglobulin.Examples of cytokine receptor modulators include, but are not limitedto, soluble cytokine receptors (e.g., the extracellular domain of aTNF-α receptor or a fragment thereof, the extracellular domain of anIL-1β receptor or a fragment thereof, and the extracellular domain of anIL-6 receptor or a fragment thereof), cytokines or fragments thereof(e.g., interleukin (IL)-2, IL-3, IL-4, IL-5, IL-6, IL-7, IL-8, IL-9,IL-10, IL-11, IL-12, IL-15, TNF-α, interferon (IFN)-α, IFN-β, IFN-γ, andGM-CSF), anti-cytokine receptor antibodies (e.g., anti-IFN receptorantibodies, anti-IL-2 receptor antibodies (e.g., Zenapax (Protein DesignLabs)), anti-IL-4 receptor antibodies, anti-IL-6 receptor antibodies,anti-IL-10 receptor antibodies, and anti-IL-12 receptor antibodies),anti-cytokine antibodies (e.g., anti-IFN antibodies, anti-TNF-αantibodies, anti-IL-1β antibodies, anti-IL-6 antibodies, anti-IL-8antibodies (e.g., ABX-IL-8 (Abgenix)), and anti-IL-12 antibodies).

The TLR7 ligands or TLR ligand prodrugs of the invention can beadministered or formulated in combination with an agent which inhibitsviral enzymes, including but not limited to inhibitors of HCV protease,such as BILN 2061 and inhibitors of NS5b polymerase such as NM107 andits prodrug NM283 (Idenix Pharmaceuticals, Inc., Cambridge, Mass.).

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with an agent which inhibitsHCV polymerase such as those described in Wu, Curr Drug Targets InfectDisord. 2003; 3(3):207-19 or in combination with compounds that inhibitthe helicase function of the virus such as those described in Bretner M,et al Nucleosides Nucleotides Nucleic Acids. 2003; 22(5-8): 1531, orwith inhibitors of other HCV specific targets such as those described inZhang X. IDrugs. 2002; 5(2):154-8.

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with an agent that inhibitsviral replication.

The TLR7 ligands or TLR ligand prodrugs of the invention can beadministered or formulated in combination with cytokines. Examples ofcytokines include, but are not limited to, interleukin-2 (IL-2),interleukin-3 (IL-3), interleukin-4 (IL-4), interleukin-5 (IL-5),interleukin-6 (IL-6), interleukin-7 (IL-7), interleukin-9 (IL-9),interleukin-10 (IL-10), interleukin-12 (IL-12), interleukin 15 (IL-15),interleukin 18 (IL-18), platelet derived growth factor (PDGF),erythropoietin (Epo), epidermal growth factor (EGF), fibroblast growthfactor (FGF), granulocyte macrophage stimulating factor (GM-CSF),granulocyte colony stimulating factor (G-CSF), macrophage colonystimulating factor (M-CSF), prolactin, and interferon (IFN), e.g.,IFN-alpha, and IFN-gamma).

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with hormones. Examples ofhormones include, but are not limited to, luteinizing hormone releasinghormone (LHRH), growth hormone (GH), growth hormone releasing hormone,ACTH, somatostatin, somatotropin, somatomedin, parathyroid hormone,hypothalamic releasing factors, insulin, glucagon, enkephalins,vasopressin, calcitonin, heparin, low molecular weight heparins,heparinoids, synthetic and natural opioids, insulin thyroid stimulatinghormones, and endorphins.

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with β-interferons whichinclude, but are not limited to, interferon beta-1a, interferon beta-1b.

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with α-interferons whichinclude, but are not limited to, interferon alpha-1, interferon alpha-2a(roferon), interferon alpha-2b, intron, Peg-Intron, Pegasys, consensusinterferon (infergen) and albuferon.

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with an absorption enhancer,particularly those which target the lymphatic system, including, but notlimited to sodium glycocholate; sodium caprate;N-lauryl-γ-D-maltopyranoside; EDTA; mixed micelle; and those reported inMuranishi Crit. Rev. Ther. Drug Carrier Syst., 7-1-33, which is herebyincorporated by reference in its entirety. Other known absorptionenhancers can also be used. Thus, the invention also encompasses apharmaceutical composition comprising one or more TLR7 ligand prodrugsof the invention and one or more absorption enhancers.

The TLR7 ligands or TLR7 ligand prodrugs of the invention can beadministered or formulated in combination with an alkylating agent.Examples of alkylating agents include, but are not limited to nitrogenmustards, ethylenimines, methylmelamines, alkyl sulfonates,nitrosoureas, triazenes, mechlorethamine, cyclophosphamide, ifosfamide,melphalan, chlorambucil, hexamethylmelaine, thiotepa, busulfan,carmustine, streptozocin, dacarbazine and temozolomide.

The compounds of the invention and the other therapeutics agent can actadditively or, more preferably, synergistically. In a preferredembodiment, a composition comprising a compound of the invention isadministered concurrently with the administration of another therapeuticagent, which can be part of the same composition or in a differentcomposition from that comprising the compounds of the invention. Inanother embodiment, a compound of the invention is administered prior toor subsequent to administration of another therapeutic agent. In aseparate embodiment, a compound of the invention is administered to apatient who has not previously undergone or is not currently undergoingtreatment with another therapeutic agent, particularly an antiviralagent.

In one embodiment, the methods of the invention comprise theadministration of one or more TLR7 ligands or TLR7 ligand prodrugs ofthe invention without an additional therapeutic agent.

Pharmaceutical Compositions and Dosage Forms

Pharmaceutical compositions and single unit dosage forms comprising aTLR7 ligand or prodrug of the invention, or a pharmaceuticallyacceptable salt, hydrate or stereoisomer thereof, are also encompassedby the invention. Individual dosage forms of the invention may besuitable for oral, mucosal (including sublingual, buccal, rectal, nasal,or vaginal), parenteral (including subcutaneous, intramuscular, bolusinjection, intraarterial, or intravenous), transdermal, or topicaladministration. Pharmaceutical compositions and dosage forms of theinvention typically also comprise one or more pharmaceuticallyacceptable excipients. Sterile dosage forms are also contemplated.

In an alternative embodiment, a pharmaceutical composition encompassedby this embodiment includes a TLR7 ligand or prodrug of the invention,or a pharmaceutically acceptable salt, hydrate or stereoisomer thereof,and at least one additional therapeutic agent. Examples of additionaltherapeutic agents include, but are not limited to, those listed abovein section 5.2.2.

The composition, shape, and type of dosage forms of the invention willtypically vary depending on their use. For example, a dosage form usedin the acute treatment of a disease or a related disease may containlarger amounts of one or more of the active ingredients it comprisesthan a dosage form used in the chronic treatment of the same disease.Similarly, a parenteral dosage form may contain smaller amounts of oneor more of the active ingredients it comprises than an oral dosage formused to treat the same disease or disorder.

These and other ways in which specific dosage forms encompassed by thisinvention will vary from one another will be readily apparent to thoseskilled in the art. See, e.g., Remington's Pharmaceutical Sciences, 18thed., Mack Publishing, Easton Pa. (1990). Examples of dosage formsinclude, but are not limited to: tablets; caplets; capsules, such assoft elastic gelatin capsules; cachets; troches; lozenges; dispersions;suppositories; ointments; cataplasms (poultices); pastes; powders;dressings; creams; plasters; solutions; patches; aerosols (e.g., nasalsprays or inhalers); gels; liquid dosage forms suitable for oral ormucosal administration to a patient, including suspensions (e.g.,aqueous or non-aqueous liquid suspensions, oil-in-water emulsions, or awater-in-oil liquid emulsions), solutions, and elixirs; liquid dosageforms suitable for parenteral administration to a patient; and sterilesolids (e.g., crystalline or amorphous solids) that can be reconstitutedto provide liquid dosage forms suitable for parenteral administration toa patient.

Typical pharmaceutical compositions and dosage forms comprise one ormore carriers, excipients or diluents. Suitable excipients are wellknown to those skilled in the art of pharmacy, and non-limiting examplesof suitable excipients are provided herein. Whether a particularexcipient is suitable for incorporation into a pharmaceuticalcomposition or dosage form depends on a variety of factors well known inthe art including, but not limited to, the way in which the dosage formwill be administered to a patient. For example, oral dosage forms suchas tablets may contain excipients not suited for use in parenteraldosage forms. The suitability of a particular excipient may also dependon the specific active ingredients in the dosage form.

This invention further encompasses anhydrous pharmaceutical compositionsand dosage forms comprising active ingredients, since water canfacilitate the degradation of some compounds. For example, the additionof water (e.g., 5%) is widely accepted in the pharmaceutical arts as ameans of simulating long-term storage in order to determinecharacteristics such as shelf-life or the stability of formulations overtime. See, e.g., Jens T. Carstensen, Drug Stability: Principles &Practice, 2d. Ed., Marcel Dekker, NY, N.Y., 1995, pp. 379-80. In effect,water and heat accelerate the decomposition of some compounds. Thus, theeffect of water on a formulation can be of great significance sincemoisture and/or humidity are commonly encountered during manufacture,handling, packaging, storage, shipment, and use of formulations.

Anhydrous pharmaceutical compositions and dosage forms of the inventioncan be prepared using anhydrous or low moisture containing ingredientsand low moisture or low humidity conditions.

An anhydrous pharmaceutical composition should be prepared and storedsuch that its anhydrous nature is maintained. Accordingly, anhydrouscompositions are preferably packaged using materials known to preventexposure to water such that they can be included in suitable formularykits. Examples of suitable packaging include, but are not limited to,hermetically sealed foils, plastics, unit dose containers (e.g., vials),blister packs, and strip packs.

The invention further encompasses pharmaceutical compositions and dosageforms that comprise one or more compounds that reduce the rate by whichan active ingredient will decompose. Such compounds, which are referredto herein as “stabilizers,” include, but are not limited to,antioxidants such as ascorbic acid, pH buffers, or salt buffers.

Like the amounts and types of excipients, the amounts and specific typesof active ingredients in a dosage form may differ depending on factorssuch as, but not limited to, the route by which it is to be administeredto patients. However, typical dosage forms of the invention compriseTLR7 ligand prodrugs of the invention, or a pharmaceutically acceptablesalt, hydrate, or stereoisomers thereof comprise 0.1 mg to 1500 mg perunit to provide doses of about 0.01 to 200 mg/kg per day.

Oral Dosage Forms

Pharmaceutical compositions of the invention that are suitable for oraladministration can be presented as discrete dosage forms, such as, butare not limited to, tablets (e.g., chewable tablets), caplets, capsules,and liquids (e.g., flavored syrups). Such dosage forms containpredetermined amounts of active ingredients, and may be prepared bymethods of pharmacy well known to those skilled in the art. Seegenerally, Remington's Pharmaceutical Sciences, 18th ed., MackPublishing, Easton Pa. (1990).

Typical oral dosage forms of the invention are prepared by combining theactive ingredient(s) in an intimate admixture with at least oneexcipient according to conventional pharmaceutical compoundingtechniques. Excipients can take a wide variety of forms depending on theform of preparation desired for administration. For example, excipientssuitable for use in oral liquid or aerosol dosage forms include, but arenot limited to, water, glycols, oils, alcohols, flavoring agents,preservatives, and coloring agents. Examples of excipients suitable foruse in solid oral dosage forms (e.g., powders, tablets, capsules, andcaplets) include, but are not limited to, starches, sugars,micro-crystalline cellulose, diluents, granulating agents, lubricants,binders, and disintegrating agents.

Because of their ease of administration, tablets and capsules representthe most advantageous oral dosage unit forms, in which case solidexcipients are employed. If desired, tablets can be coated by standardaqueous or nonaqueous techniques. Such dosage forms can be prepared byany of the methods of pharmacy. In general, pharmaceutical compositionsand dosage forms are prepared by uniformly and intimately admixing theactive ingredients with liquid carriers, finely divided solid carriers,or both, and then shaping the product into the desired presentation ifnecessary.

For example, a tablet can be prepared by compression or molding.Compressed tablets can be prepared by compressing in a suitable machinethe active ingredients in a free-flowing form such as powder orgranules, optionally mixed with an excipient. Molded tablets can be madeby molding in a suitable machine a mixture of the powdered compoundmoistened with an inert liquid diluent.

Examples of excipients that can be used in oral dosage forms of theinvention include, but are not limited to, binders, fillers,disintegrants, and lubricants. Binders suitable for use inpharmaceutical compositions and dosage forms include, but are notlimited to, corn starch, potato starch, or other starches, gelatin,natural and synthetic gums such as acacia, sodium alginate, alginicacid, other alginates, powdered tragacanth, guar gum, cellulose and itsderivatives (e.g., ethyl cellulose, cellulose acetate, carboxymethylcellulose calcium, sodium carboxymethyl cellulose), polyvinylpyrrolidone, methyl cellulose, pre-gelatinized starch, hydroxypropylmethyl cellulose, (e.g., Nos. 2208, 2906, 2910), microcrystallinecellulose, and mixtures thereof.

Examples of fillers suitable for use in the pharmaceutical compositionsand dosage forms disclosed herein include, but are not limited to, talc,calcium carbonate (e.g., granules or powder), microcrystallinecellulose, powdered cellulose, dextrates, kaolin, mannitol, silicicacid, sorbitol, starch, pre-gelatinized starch, and mixtures thereof.The binder or filler in pharmaceutical compositions of the invention istypically present in from about 50 to about 99 weight percent of thepharmaceutical composition or dosage form.

Suitable forms of microcrystalline cellulose include, but are notlimited to, the materials sold as AVICEL-PH-101, AVICEL-PH-103 AVICELRC-581, AVICEL-PH-105 (available from FMC Corporation, American ViscoseDivision, Avicel Sales, Marcus Hook, PA), and mixtures thereof. Aspecific binder is a mixture of microcrystalline cellulose and sodiumcarboxymethyl cellulose sold as AVICEL RC-581. Suitable anhydrous or lowmoisture excipients or additives include AVICEL-PH-103™ and Starch 1500LM.

Disintegrants are used in the compositions of the invention to providetablets that disintegrate when exposed to an aqueous environment.Tablets that contain too much disintegrant may disintegrate in storage,while those that contain too little may not disintegrate at a desiredrate or under the desired conditions. Thus, a sufficient amount ofdisintegrant that is neither too much nor too little to detrimentallyalter the release of the active ingredients should be used to form solidoral dosage forms of the invention. The amount of disintegrant usedvaries based upon the type of formulation, and is readily discernible tothose of ordinary skill in the art. Typical pharmaceutical compositionscomprise from about 0.5 to about 15 weight percent of disintegrant,specifically from about 1 to about 5 weight percent of disintegrant.

Disintegrants that can be used in pharmaceutical compositions and dosageforms of the invention include, but are not limited to, agar-agar,alginic acid, calcium carbonate, microcrystalline cellulose,croscarmellose sodium, crospovidone, polacrilin potassium, sodium starchglycolate, potato or tapioca starch, pre-gelatinized starch, otherstarches, clays, other algins, other celluloses, gums, and mixturesthereof.

Lubricants that can be used in pharmaceutical compositions and dosageforms of the invention include, but are not limited to, calciumstearate, magnesium stearate, mineral oil, light mineral oil, glycerin,sorbitol, mannitol, polyethylene glycol, other glycols, stearic acid,sodium lauryl sulfate, talc, hydrogenated vegetable oil (e.g., peanutoil, cottonseed oil, sunflower oil, sesame oil, olive oil, corn oil, andsoybean oil), zinc stearate, ethyl oleate, ethyl laureate, agar, andmixtures thereof. Additional lubricants include, for example, a syloidsilica gel (AEROSIL 200, manufactured by W.R. Grace Co. of Baltimore,Md.), a coagulated aerosol of synthetic silica (marketed by Degussa Co.of Plano, Tex.), CAB-O-SIL (a pyrogenic silicon dioxide product sold byCabot Co. of Boston, Mass.), and mixtures thereof. If used at all,lubricants are typically used in an amount of less than about 1 weightpercent of the pharmaceutical compositions or dosage forms into whichthey are incorporated.

Delayed Release Dosage Forms

Active ingredients of the invention can be administered by controlledrelease means or by delivery devices that are well known to those ofordinary skill in the art. Examples include, but are not limited to,those described in U.S. Pat. Nos. 3,845,770; 3,916,899; 3,536,809;3,598,123; and 4,008,719, 5,674,533, 5,059,595, 5,591,767, 5,120,548,5,073,543, 5,639,476, 5,354,556, and 5,733,566, each of which isincorporated herein by reference. Such dosage forms can be used toprovide slow or controlled-release of one or more active ingredientsusing, for example, hydropropylmethyl cellulose, other polymer matrices,gels, permeable membranes, osmotic systems, multilayer coatings,microparticles, liposomes, microspheres, or a combination thereof toprovide the desired release profile in varying proportions. Suitablecontrolled-release formulations known to those of ordinary skill in theart, including those described herein, can be readily selected for usewith the active ingredients of the invention. The invention thusencompasses single unit dosage forms suitable for oral administrationsuch as, but not limited to, tablets, capsules, gelcaps, and capletsthat are adapted for controlled-release.

All controlled-release pharmaceutical products have a common goal ofimproving drug therapy over that achieved by their non-controlledcounterparts. Ideally, the use of an optimally designedcontrolled-release preparation in medical treatment is characterized bya minimum of drug substance being employed to cure or control thecondition in a minimum amount of time. Advantages of controlled-releaseformulations include extended activity of the drug, reduced dosagefrequency, and increased patient compliance. In addition,controlled-release formulations can be used to affect the time of onsetof action or other characteristics, such as blood levels of the drug,and can thus affect the occurrence of side (e.g., adverse) effects.

Most controlled-release formulations are designed to initially releasean amount of drug (active ingredient) that promptly produces the desiredtherapeutic effect, and gradually and continually release other amountsof drug to maintain this level of therapeutic or prophylactic effectover an extended period of time. In order to maintain this constantlevel of drug in the body, the drug must be released from the dosageform at a rate that will replace the amount of drug being metabolizedand excreted from the body. Controlled-release of an active ingredientcan be stimulated by various conditions including, but not limited to,pH, temperature, enzymes, water, or other physiological conditions orcompounds.

Parenteral Dosage Forms

Parenteral dosage forms can be administered to patients by variousroutes including, but not limited to, subcutaneous, intravenous(including bolus injection), intramuscular, and intraarterial. Becausetheir administration typically bypasses patients' natural defensesagainst contaminants, parenteral dosage forms are preferably sterile orcapable of being sterilized prior to administration to a patient.Examples of parenteral dosage forms include, but are not limited to,solutions ready for injection, dry and/or lyophylized products ready tobe dissolved or suspended in a pharmaceutically acceptable vehicle forinjection (reconstitutable powders), suspensions ready for injection,and emulsions.

Suitable vehicles that can be used to provide parenteral dosage forms ofthe invention are well known to those skilled in the art. Examplesinclude, but are not limited to: Water for Injection USP; aqueousvehicles such as, but not limited to, Sodium Chloride Injection,Ringer's Injection, Dextrose Injection, Dextrose and Sodium ChlorideInjection, and Lactated Ringer's Injection; water-miscible vehicles suchas, but not limited to, ethyl alcohol, polyethylene glycol, andpolypropylene glycol; and non-aqueous vehicles such as, but not limitedto, corn oil, cottonseed oil, peanut oil, sesame oil, ethyl oleate,isopropyl myristate, and benzyl benzoate.

Compounds that increase the solubility of one or more of the activeingredients disclosed herein can also be incorporated into theparenteral dosage forms of the invention.

Transdermal Dosage Forms

Transdermal dosage forms include “reservoir type” or “matrix type”patches, which can be applied to the skin and worn for a specific periodof time to permit the penetration of a desired amount of activeingredients.

Suitable excipients (e.g., carriers and diluents) and other materialsthat can be used to provide transdermal and topical dosage formsencompassed by this invention are well known to those skilled in thepharmaceutical arts, and depend on the particular tissue to which agiven pharmaceutical composition or dosage form will be applied. Withthat fact in mind, typical excipients include, but are not limited to,water, acetone, ethanol, ethylene glycol, propylene glycol,butane-1,3-diol, isopropyl myristate, isopropyl palmitate, mineral oil,and mixtures thereof.

Depending on the specific tissue to be treated, additional componentsmay be used prior to, in conjunction with, or subsequent to treatmentwith active ingredients of the invention. For example, penetrationenhancers can be used to assist in delivering the active ingredients tothe tissue. Suitable penetration enhancers include, but are not limitedto: acetone; various alcohols such as ethanol, oleyl, andtetrahydrofuryl; alkyl sulfoxides such as dimethyl sulfoxide; dimethylacetamide; dimethyl formamide; polyethylene glycol; pyrrolidones such aspolyvinylpyrrolidone; Kollidon grades (Povidone, Polyvidone); urea; andvarious water-soluble or insoluble sugar esters such as Tween 80(polysorbate 80) and Span 60 (sorbitan monostearate).

The pH of a pharmaceutical composition or dosage form, or of the tissueto which the pharmaceutical composition or dosage form is applied, mayalso be adjusted to improve delivery of one or more active ingredients.Similarly, the polarity of a solvent carrier, its ionic strength, ortonicity can be adjusted to improve delivery. Compounds such asstearates can also be added to pharmaceutical compositions or dosageforms to advantageously alter the hydrophilicity or lipophilicity of oneor more active ingredients so as to improve delivery. In this regard,stearates can serve as a lipid vehicle for the formulation, as anemulsifying agent or surfactant, and as a delivery-enhancing orpenetration-enhancing agent. Different salts, hydrates or solvates ofthe active ingredients can be used to further adjust the properties ofthe resulting composition.

Topical Dosage Forms

Topical dosage forms of the invention include, but are not limited to,creams, lotions, ointments, gels, solutions, emulsions, suspensions, orother forms known to one of skill in the art. See, e.g., Remington'sPharmaceutical Sciences, 18th eds., Mack Publishing, Easton Pa. (1990);and Introduction to Pharmaceutical Dosage Forms, 4th ed., Lea & Febiger,Philadelphia (1985).

Suitable excipients (e.g., carriers and diluents) and other materialsthat can be used to provide transdermal and topical dosage formsencompassed by this invention are well known to those skilled in thepharmaceutical arts, and depend on the particular tissue to which agiven pharmaceutical composition or dosage form will be applied. Withthat fact in mind, typical excipients include, but are not limited to,water, acetone, ethanol, ethylene glycol, propylene glycol,butane-1,3-diol, isopropyl myristate, isopropyl palmitate, mineral oil,and mixtures thereof.

Depending on the specific tissue to be treated, additional componentsmay be used prior to, in conjunction with, or subsequent to treatmentwith active ingredients of the invention. For example, penetrationenhancers can be used to assist in delivering the active ingredients tothe tissue. Suitable penetration enhancers include, but are not limitedto: acetone; various alcohols such as ethanol, oleyl, andtetrahydrofuryl; alkyl sulfoxides such as dimethyl sulfoxide; dimethylacetamide; dimethyl formamide; polyethylene glycol; pyrrolidones such aspolyvinylpyrrolidone; Kollidon grades (Povidone, Polyvidone); urea; andvarious water-soluble or insoluble sugar esters such as Tween 80(polysorbate 80) and Span 60 (sorbitan monostearate).

Mucosal Dosage Forms

Mucosal dosage forms of the invention include, but are not limited to,ophthalmic solutions, sprays and aerosols, or other forms known to oneof skill in the art. See, e.g., Remington's Pharmaceutical Sciences,18th eds., Mack Publishing, Easton Pa. (1990); and Introduction toPharmaceutical Dosage Forms, 4th ed., Lea & Febiger, Philadelphia(1985). Dosage forms suitable for treating mucosal tissues within theoral cavity can be formulated as mouthwashes or as oral gels. In oneembodiment, the aerosol comprises a carrier. In another embodiment, theaerosol is carrier free.

The TLR7 ligands or TLR7 ligand prodrugs of the invention may also beadministered directly to the lung by inhalation. For administration byinhalation, a TLR7 ligand can be conveniently delivered to the lung by anumber of different devices. For example, a Metered Dose Inhaler (“MDI”)which utilizes canisters that contain a suitable low boiling propellant,e.g., dichlorodifluoromethane, trichlorofluoromethane,dichlorotetrafluoroethane, carbon dioxide or other suitable gas can beused to deliver a TLR7 ligand directly to the lung. MDI devices areavailable from a number of suppliers such as 3M Corporation, Aventis,Boehringer Ingleheim, Forest Laboratories, Glaxo-Wellcome, ScheringPlough and Vectura.

Alternatively, a Dry Powder Inhaler (DPI) device can be used toadminister a TLR7 ligand to the lung (see, e.g., Raleigh et al., Proc.Amer. Assoc. Cancer Research Annual Meeting, 1999, 40, 397, which isherein incorporated by reference). DPI devices typically use a mechanismsuch as a burst of gas to create a cloud of dry powder inside acontainer, which can then be inhaled by the patient. DPI devices arealso well known in the art and can be purchased from a number of vendorswhich include, for example, Fisons, Glaxo-Wellcome, Inhale TherapeuticSystems, ML Laboratories, Qdose and Vectura. A popular variation is themultiple dose DPI (“MDDPI”) system, which allows for the delivery ofmore than one therapeutic dose. MDDPI devices are available fromcompanies such as AstraZeneca, GlaxoWellcome, IVAX, Schering Plough,SkyePharma and Vectura. For example, capsules and cartridges of gelatinfor use in an inhaler or insufflator can be formulated containing apowder mix of the compound and a suitable powder base such as lactose orstarch for these systems.

Another type of device that can be used to deliver a TLR7 ligand or TLR7ligand prodrug to the lung is a liquid spray device supplied, forexample, by Aradigm Corporation. Liquid spray systems use extremelysmall nozzle holes to aerosolize liquid drug formulations that can thenbe directly inhaled into the lung.

In a preferred embodiment, a nebulizer device is used to deliver TLR7ligands or TLR ligand prodrugs to the lung. Nebulizers create aerosolsfrom liquid drug formulations by using, for example, ultrasonic energyto form fine particles that can be readily inhaled (See e.g., Verschoyleet al., British J. Cancer, 1999, 80, Suppl 2, 96, which is hereinincorporated by reference). Examples of nebulizers include devicessupplied by Sheffield/Systemic Pulmonary Delivery Ltd, Aventis, andBatelle Pulmonary Therapeutics. See U.S. Pat. Nos. 5,954,047; 5,950,619;5,970,974, which are herein incorporated by reference.

In a particularly preferred embodiment, an electrohydrodynamic (“EHD”)aerosol device is used to deliver TLR7 ligands and TLR7 ligand prodrugsto the lung. EHD aerosol devices use electrical energy to aerosolizeliquid drug solutions or suspensions (see, e.g., Noakes et al., U.S.Pat. No. 4,765,539; Coffee, U.S. Pat. No. 4,962,885; Coffee, PCTApplication, WO 94/12285; Coffee, PCT Application, WO 94/14543; Coffee,PCT Application, WO 95/26234, Coffee, PCT Application, WO 95/26235,Coffee, PCT Application, WO 95/32807, which are herein incorporated byreference). The electrochemical properties of the TLR7 ligands and TLR7ligand prodrugs formulation may be important parameters to optimize whendelivering this drug to the lung with an EHD aerosol device and suchoptimization is routinely performed by one of skill in the art. EHDaerosol devices may more efficiently delivery drugs to the lung thanexisting pulmonary delivery technologies. Other methods ofintra-pulmonary delivery of TLR7 ligand and TLR7 ligand prodrugs will beknown to the skilled artisan and are within the scope of the invention.

Liquid drug formulations suitable for use with nebulizers and liquidspray devices and EHD aerosol devices will typically include a TLR7ligand or TLR7 ligand prodrug with a pharmaceutically acceptablecarrier. Preferably, the pharmaceutically acceptable carrier is a liquidsuch as alcohol, water, polyethylene glycol or a perfluorocarbon.Optionally, another material may be added to alter the aerosolproperties of the solution or suspension of the TLR7 ligand or prodrugof a TLR7 ligand. Preferably, this material is liquid such as analcohol, glycol, polyglycol or a fatty acid. Other methods offormulating liquid drug solutions or suspension suitable for use inaerosol devices are known to those of skill in the art (see, e.g.,Biesalski, U.S. Pat. Nos. 5,112,598; Biesalski, 5,556,611, which areherein incorporated by reference) A TLR7 ligand or prodrug of a TLR7ligand can also be formulated in rectal or vaginal compositions such assuppositories or retention enemas, e.g., containing conventionalsuppository bases such as cocoa butter or other glycerides.

In addition to the formulations described previously, a TLR7 ligand orTLR7 ligand prodrug can also be formulated as a depot preparation. Suchlong acting formulations can be administered by implantation (forexample subcutaneously or intramuscularly) or by intramuscularinjection. Thus, for example, the compounds can be formulated withsuitable polymeric or hydrophobic materials (for example, as an emulsionin an acceptable oil) or ion exchange resins, or as sparingly solublederivatives, for example, as a sparingly soluble salt.

Alternatively, other pharmaceutical delivery systems can be employed.Liposomes and emulsions are well known examples of delivery vehiclesthat can be used to deliver TLR7 ligands and TLR7 ligand prodrugs.Certain organic solvents such as dimethylsulfoxide can also be employed,although usually at the cost of greater toxicity. A TLR7 ligand orprodrug of a TLR7 ligand can also be delivered in a controlled releasesystem. In one embodiment, a pump can be used (Sefton, CRC Crit. RefBiomed Eng., 1987, 14, 201; Buchwald et al., Surgery, 1980, 88, 507;Saudek et al., N. Engl. J. Med., 1989, 321, 574). In another embodiment,polymeric materials can be used (see Medical Applications of ControlledRelease, Langer and Wise (eds.), CRC Pres., Boca Raton, Fla. (1974);Controlled Drug Bioavailability, Drug Product Design and Performance,Smolen and Ball (eds.), Wiley, New York (1984); Ranger and Peppas, J.Macromol. Sci. Rev. Macromol. Chem., 1983, 23, 61; see also Levy et al.,Science, 1985, 228, 190; During et al., Ann. Neurol., 1989,25,351;Howard et al., 1989, J. Neurosurg. 71, 105). In yet another embodiment,a controlled-release system can be placed in proximity of the target ofthe compounds of the invention e.g., the lung, thus requiring only afraction of the systemic dose (see, e.g., Goodson, in MedicalApplications of Controlled Release, supra, vol. 2, pp. 115 (1984)).Other controlled-release system can be used (see, e.g. Langer, Science,1990, 249, 1527).

Suitable excipients (e.g., carriers and diluents) and other materialsthat can be used to provide mucosal dosage forms encompassed by thisinvention are well known to those skilled in the pharmaceutical arts,and depend on the particular site or method which a given pharmaceuticalcomposition or dosage form will be administered. With that fact in mind,typical excipients include, but are not limited to, water, ethanol,ethylene glycol, propylene glycol, butane-1,3-diol, isopropyl myristate,isopropyl palmitate, mineral oil, and mixtures thereof, which arenon-toxic and pharmaceutically acceptable. Examples of such additionalingredients are well known in the art. See, e.g., Remington'sPharmaceutical Sciences, 18th eds., Mack Publishing, Easton Pa. (1990).

The pH of a pharmaceutical composition or dosage form, or of the tissueto which the pharmaceutical composition or dosage form is applied, canalso be adjusted to improve delivery of one or more active ingredients.Similarly, the polarity of a solvent carrier, its ionic strength, ortonicity can be adjusted to improve delivery. Compounds such asstearates can also be added to pharmaceutical compositions or dosageforms to advantageously alter the hydrophilicity or lipophilicity of oneor more active ingredients so as to improve delivery. In this regard,stearates can serve as a lipid vehicle for the formulation, as anemulsifying agent or surfactant, and as a delivery-enhancing orpenetration-enhancing agent. Different salts, hydrates or solvates ofthe active ingredients can be used to further adjust the properties ofthe resulting composition.

Kits

The invention provides a pharmaceutical pack or kit comprising one ormore containers comprising a TLR7 ligand prodrug useful for thetreatment or prevention of a Hepatitis C virus infection. In otherembodiments, the invention provides a pharmaceutical pack or kitcomprising one or more containers comprising a TLR7 ligand prodruguseful for the treatment or prevention of a Hepatitis C virus infectionand one or more containers comprising an additional therapeutic agent,including but not limited to those listed in section 5.2.2 above, inparticular an antiviral agent, an interferon, an agent which inhibitsviral enzymes, or an agent which inhibits viral replication, preferablythe additional therapeutic agent is HCV specific or demonstratesanti-HCV activity.

The invention also provides a pharmaceutical pack or kit comprising oneor more containers comprising one or more of the ingredients of thepharmaceutical compositions of the invention. Optionally associated withsuch container(s) can be a notice in the form prescribed by agovernmental agency regulating the manufacture, use or sale ofpharmaceuticals or biological products, which notice reflects approvalby the agency of manufacture, use or sale for human administration.

Assays

The TLR7 ligands, TLR ligand prodrugs, compositions and dosage forms ofthe invention can be tested in vitro or in vivo by a variety of methodsknown in the art to test activity. See, for example, the methodsdiscussed below and used throughout the examples.

A range of assays for the purpose of evaluating TLR7 activity areavailable, and are described in the following publications, each ofwhich is incorporated-by-reference: Hirota et al., J. Med. Chem., 45,5419-5422 (2002); and Akira S. et al., Immunology Letters, 85, 85-95(2003). For example, one system useful for the assay of TLR7 ligands iswhere the gene for TLR7 is cloned by methods known to those of skill inthe art and transfected into an appropriate cell type such that TLR7 isexpressed and coupled to a NFkB-luciferase reporter plasmid. In thiscell system, exposure to TLR7 ligand prodrugs in cell culture results ina measurable luminescence signal. See, e.g., Lee et al., Proc. Nat.Acad. USA, 100, 6646-6651 (2003); Hemmi et al., Nat. Immunol., 3,196-200 (2002); and Jurk et al., Nat. Immunol., 3, 499 (2002) (whereinthe Lee et al., Hemmi et al., and Jurk et al., references are allincorporated herein by reference).

Another example of an in vitro method is to expose human peripheralblood mononuclear cells (PBMC) to the candidate TLR7 ligand prodrug fora predetermined interval (e.g., 2 hours to 24 hours), followed bymeasurement of immunologic activity. Such immunologic activity mayinclude induction of the synthesis of cytokines, which can be measuredin the culture supernate by ELISA assay of the cytokine protein, such asa Type 1 interferon (interferon alpha, interferon beta) or Type 2interferon (interferon gamma). Alternatively, the PBMC can be harvestedafter incubation with the candidate TLR7 ligand prodrug, the PBMC RNAextracted, and the level of induction of immune system genes determinedby RNAse protection assays of the extracted RNA. Genes typically inducedinclude 2′5′-OAS, or interferon gamma, but a range of cytokines can bemeasured. See, e.g., Hirota et al., J. Med. Chem., 45, 5419-5422 (2002).

RNAse protection assays (RPA) are a method known in the art wherein RNAanalytes are quantitated by first hybridizing them to a radioalabeledRNA sequence specific for the analyte RNA, followed by digestion withenzymes that selectively degrade single stranded RNA. The sample is thensubmitted to gel electrophoresis under conditions that resolve thehybridized, protected double stranded RNA. The gel is thenautoradiographed to reveal the location and intensity of the bands.These can be quantitated by methods well known in the art. Multipleanalyte RNA species can be simultaneously assayed, if the protectedfragments are sufficiently different in size to allow their separationby gel electrophoresis. Comparison of the levels of an analyte RNA tocontrol RNA species that is expressed at constant levels in cellsprovides an internal control that enable changes in levels of theanalyte RNA species to be monitored even if the total amount of RNAvaries. Such RNAse protection assays can be performed as follows:

RNA is purified from PMBC pellets using the “RNAeasy” kit (Qiagen),according to the manufacturer's instructions. Template sets may beobtained from PharMingen (BD Biosciences); a useful set that iscommercially available from this supplier contains materials allowingthe assay of TNF-a, IL12 p 35, IP10, IL-1a, IL-1b, IL-6, Interferongamma, and the control RNA species L32 and GAPDH. This template setcontains DNA that is appropriate for synthesis of the proper RNA probefor each of the listed genes.

Probe synthesis is performed using the PharMingen in vitro transcriptionkit provided in the kit. The reaction contains RNase inhibitor;transcription buffer; 50 ng of the tempate set; 0.1375 mM of each ofrGTP, rCTP, rATP; 0.003 mM rUTP; 10 mM DTT, 0.010 mCi of [alpha 32P]UTP, and 20 Units of T7 RNA polymerase in a volume of 20 microliters.The reaction mixture is incubated for one hour at 37° C., and thenstopped by addition of 2 units of RNAse free DNAse, with an additionalincubation of 30 minutes at 37° C. The RNA probes synthesized in thisincubation are extracted once with 5.2 mM EDTA, 25 μl of Tris Saturatedphenol, 25 μL of chloroform, and 4 μg of yeast tRNA, and then extractedwith 50 μL of chloroform. The RNA is precipitated by addition of 50 μLof 4M ammonium acetate and 250 μL of ice-cold 100% ethanol, and afterincubation at −80° C. for 30 minutes the preparation is centrifuged athigh speed for 30 minutes. The pellet is washed in 100% ethanol, andafter removal of the ethanol the probe is resuspended and used in theRNAse protection incubation.

The RNAse protection assay uses the probe material prepared above andRNA extracted from PBMC. The PBMC RNA is washed in 100% ethanol,quantitated by absorbance at 260 nm. The RPA is performed as describedin the protocol provided in the PharMingen RiboQuant kit. Eight 1 μL ofthe PBMC RNA samples are mixed with the 2 μL of the probe set in athin-walled PCR tube, mixed well, briefly centrifuged and then overlaidwith mineral oil. The tube is then placed in a 90° C. PCR block, cooledto 56° C., and incubated for 16 hours. The samples are then cooled to37° C. and RNAse A and RNAse TI are added. The mixture is incubated for45 minutes at 30° C., and the reaction stopped with a mix of protease Kand yeast tRNA. The RNA is extracted with phenol-chloroform, and thenprecipitated from the phenol-chloroform with ammonium acetate-ethanol.The pellet is washed with ethanol and resuspended in buffer forelectrophoresis. The samples are analysed by gel electrophoresis bymethods well known in molecular biology.

A number of assays may be employed in accordance with the presentinvention in order to determine the degree of anti-viral activity of acompound of the invention such as cell culture, animal models, andadministration to human subjects. The assays described herein may beused to assay viral growth over time to determine the growthcharacteristics of a virus in the presence of a compound of theinvention.

In another embodiment, a virus and a compound of the invention areadministered to animal subjects susceptible to infection with the virus.The incidence, severity, length, virus load, mortality rate ofinfection, etc. can be compared to the incidence, severity, length,virus load, mortality rate of infection, etc. observed when subjects areadministered the virus alone (in the absence of a compound of theinvention). Anti-virus activity of the compound of the invention isdemonstrated by a decrease in incidence, severity, length, virus load,mortality rate of infection, etc. in the presence of the compound of theinvention. In a specific embodiment, the virus and the compound of theinvention are administered to the animal subject at the same time. Inanother specific embodiment, the virus is administered to the animalsubject before the compound of the invention. In another specificembodiment, the compound of the invention is administered to the animalsubject before the virus.

In another embodiment, the growth rate of the virus can be tested bysampling biological fluids/clinical samples (e.g., nasal aspirate,throat swab, sputum, broncho-alveolar lavage, urine, saliva, blood, orserum) from human or animal subjects at multiple time pointspost-infection either in the presence or absence of a compound of theinvention and measuring levels of virus. In specific embodiments, thegrowth rate of a virus is assayed by assessing the presence of virus ina sample after growth in cell culture, growth on a permissible growthmedium, or growth in subject using any method well-known in the art, forexample, but not limited to, immunoassay (e.g., ELISA; for discussionregarding ELISAs see, e.g., Ausubel et al., eds, 1994, Current Protocolsin Molecular Biology, Vol. I, John Wiley & Sons, Inc., New York at11.2.1), immunofluorescent staining, or immunoblot analysis using anantibody which immunospecifically recognizes the virus to be assayed ordetection of a virus-specific nucleic acid (e.g., by Southern blot orRT-PCR analysis, etc.).

In a specific embodiment, viral titers can be determined by obtainingbiological fluids/clinical samples from infected cells or an infectedsubject, preparing a serial dilution of the sample and infecting amonolayer of cells that are susceptible to infection with the virus(e.g. primary cells, transformed cell lines, patient tissue samples,etc) at a dilution of the virus that allows for the emergence of singleplaques. The plaques can then be counted and the viral titer expressedas plaque forming units per milliliter of sample.

In one specific embodiment, the growth rate of a virus in a subject canbe estimated by the titer of antibodies against the virus in thesubject. Antibody serum titer can be determined by any method well-knownin the art, for example, but not limited to, the amount of antibody orantibody fragment in serum samples can be quantitated by, e.g., ELISA.

Additionally, in vivo activity of a TLR7 ligand or prodrug of a TLR7ligand can be determined by directly administering the compound to atest animal, collecting biological fluids (e.g., nasal aspirate, throatswab, sputum, broncho-alveolar lavage, urine, saliva, blood, or serum)and testing the fluid for anti-virus activity.

In embodiments where samples to be assayed for virus levels arebiological fluids/clinical samples (e.g., nasal aspirate, throat swab,sputum, broncho-alveolar lavage, urine, saliva, blood, or serum), thesamples may or may not contain in tact cells. Samples from subjectscontaining intact cells can be directly processed, whereas isolateswithout intact cells may or may not be first cultured on a permissivecell line (e.g. primary cells, transformed cell lines, patient tissuesamples, etc) or growth medium (e.g., LB broth/agar, YT broth/agar,blood agar, etc.). Cell suspensions can be cleared by centrifugation at,e.g., 300×g for 5 minutes at room temperature, followed by a PBS, pH 7.4(Ca++ and Mg++free) wash under the same conditions. Cell pellets can beresuspended in a small volume of PBS for analysis. Primary clinicalisolates containing intact cells can be mixed with PBS and centrifugedat 300×g for 5 minutes at room temperature. Mucus is removed from theinterface with a sterile pipette tip and cell pellets can be washed oncemore with PBS under the same conditions. Pellets can then be resuspendedin a small volume of PBS for analysis.

In another embodiment, a compound of the invention is administered to ahuman subject infected with a virus. The incidence, severity, length,viral load, mortality rate of infection, etc. can be compared to theincidence, severity, length, viral load, mortality rate of infection,etc. observed in human subjects infected with a virus in the absence ofa compound of the invention or in the presence of a placebo. Anti-viralactivity of the compound of the invention is demonstrated by a decreasein incidence, severity, length, viral load, mortality rate of infection,etc. in the presence of the compound of the invention. Any method knownin the art can be used to determine anti-viral activity in a subjectsuch as those described previously.

Additionally, in vivo activity of a TLR7 ligand or prodrug of TLR7ligand can be determined by directly administering the compound to ananimal or human subject, collecting biological fluids/clinical samples(e.g., nasal aspirate, throat swab, sputum, broncho-alveolar lavage,urine, saliva, blood, or serum) and testing the biologicalfluids/clinical samples for anti-viral activity (e.g., by addition tocells in culture in the presence of the virus).

The foregoing has demonstrated the pertinent and important features ofthe present invention. One of skill in the art will be appreciate thatnumerous modifications and embodiments may be devised. Therefore, it isintended that the appended claims cover all such modifications andembodiments.

6. EXAMPLES

The following examples are for the purpose of illustration only and arenot intended as limiting the scope of the invention.

6.1 TLR7 Ligand Identification

There are three known chemical classes of TLR7 ligands: guanosines,imidazoquinolines, and pyrimidines (see Section 5.2). As describedabove, additional TLR7 ligands are readily identified by known screeningmethods. For example, adenine analogs and derivatives were identified asTLR ligands by using the following screening procedure. See Tables 1 and2.

A stable HEK293-hTLR7 cell line was obtained from Invivogen (San Diego,Calif.), transfected with pNiFty2-Luc, an NF-kB inducible luciferasereporter plasmid (Invivogen) and (dual) stable transfectants selected.The resultant dual (hTLR7/pNiFty2-Luc) cell lines were functionallytested by response to loxoribine and isatoribine as measured by foldluciferase induction relative to a no drug control. The C23 line waschosen due to its satisfactory response and sensitivity profile withthese (and other) TLR7 agonists. The biological rationale which connectsTLR7 engagement and NF-kB activation has met with widespread acceptance(for a review, see Akira S. et al., Immunol Lett., 85, 85-95 (2003)) andas a consequence the HEK293-TLR-NF-kB inducible reporter system isaccepted as a standard assay which has been consistently used to assayTLR(7) agonists, in either transient or stable system format. See, e.g.,Hemmi H. et al., Nat. Immunol., 3, 196-200 (2002); Jurk M. et al., Nat.Immunol., 3,499 (2002); and Lee J. et al., Proc. Natl. Acad. Sci. USA,100, 6646-51 (2003).

For a typical C23 assay, cells are seeded at 6×10⁴ cells/well in 96 wellplates and 4-24 hours later are treated with various concentrations ofcompound. After 2-48 hours exposure the cell monolayers are lyzed withpassive lysis buffer (Promega) and the firefly luciferase assay carriedout using the luciferase assay reagent (Promega) as specified by themanufacturer. Relative luciferase activities are expressed as folds ofinduction compared to the no drug control. A two-fold induction overbackground is considered a bona fide TLR7 agonist, dependent on thisbeing a statistically significant increase.

TABLE 1 Isatoribine Activates Human TLR7 in HEK293 Assay Compoundconcentration, μM Compound No. 50 100 250 500 21 3.1 3.4 6.2 10.9 (±0.2)(±0.1) (±0.5) (±0.7)

TABLE 2 Adenine Derivative Activates Human TLR7 in HEK293 Assay Compoundconcentration, μM Compound No. 1.0 3.2 10 32 29 20.8 37.3 47.5 48.4(±1.1) (±0.5) (±0.2) (±0.4)

In Table 1, isatoribine, was added to C23 cells for forty-eight hours,and the cells were then harvested and assayed for luciferase activity.Each time-point was assayed in triplicate. The data displayed is themean fold induction compared to the no drug control, together with thestandard deviation in parentheses.

In Table 2, an adenine derivative 29 was added to C23 cells fortwenty-four hours, and the cells were then harvested and assayed forluciferase activity. Each time-point was assayed in triplicate. The datadisplayed is the mean fold induction compared to the no drug control,together with the standard deviation in parentheses.

6.2 TLR7 Ligands Tested as Anti-HCV Agents

HCV Viral Load Reduction

Isatoribine investigational drug product was supplied as a 1 mg/mLsolution in sterile normal saline contained in a 50 mL vial. Isatoribinewas administered in humans by intravenous infusion once daily for 7days, at 200, 400, 600 or 800 mg per dose. All doses were administeredby constant rate infusion over a 60-minute period, except the 800 mgdose was administered over an 80-minute period. The flow rate for eachdose was as follows: 3.33 mL/min for the 200 mg dose; 6.67 mL/min forthe 400 mg dose; 8.33 mL/min for the 500 mg dose; or 10.0 mL/min for the600 mg and 800 mg dose.

Four to twelve patients were enrolled in each of the dose groups (200mg, 400 mg, 600 mg and 800 mg per dose) and received once dailyintravenous infusions for 7 days. Prior to dosing, a blood sample wasdrawn from each patient for assessment of the genotype of the HCV virus.

Plasma HCV RNA was determined at baseline (an average of 2 pre-treatmentmeasurements taken on Day-1 or pre-treatment and on Day 1) and oncedaily prior to the start of the first daily isatoribine intravenousinfusion on Days 2 through 7 for these daily (×7 days) dosing groups.See FIG. 2. The viral load was measured by the branched DNA method(Versant™ v3.0 bDNA assay, Bayer Diagnostics). For plasma HCV RNA, themaximum change from the pre-treatment baseline was estimated usinglog-transformed values.

Plasma HCV RNA decreased over the course of isatoribine treatment, withthe larger changes generally occurring in patients who received thehigher daily doses (FIG. 2). Eight of 12 patients who receivedisatoribine 800 mg QD×7 days showed a plasma viral load decrease of morethan 0.5 log 10 units, with a mean change in these 12 patients of −0.76log 10 units and range of −2.85 to +0.21 log 10 units. This decrease inviral load was statistically significant for the 800 mg QD dose group(p=0.008). Plasma viral load declines generally reversed upon cessationof treatment.

HCV Replicon-Based Viral Bioassay

It has been demonstrated that HCV replicons are highly sensitive to theinhibitory effects of interferon-α and interferon-γ. Therefore the HCVreplicon becomes a very useful system for measuring the amount ofbiologically active interferons in supernatants from human PBMCsstimulated with a TLR7 agonist. A quantitative assay was developed whichis based on measuring the activity of the luciferase reporter gene thatwas integrated into an HCV replicon. By using this system, interferonsfrom TLR7 agonist-treated PBMCs were measured and their inhibitoryactivity was assessed using the luciferase reporter replicon.

Human PBMCs isolated from a healthy donor were placed in replicate cellculture wells (5×10⁶ cells per well). The PBMCs are incubated in theabsence of test compounds at 37° C. in a humidified atmospherecontaining 5% CO₂ for 24 hours to allow stabilization to the cultureconditions, and then the TLR7 ligand or a drug free control is added toreplicate wells containing PBMCs from the same donor. The concentrationsof TLR7 ligand may be varied to suit the particular experiment, and thePBMC cultures are then incubated at 37° C. in a humidified atmospherecontaining 5% CO₂ for eight hours. Samples of cell culture supernatantare taken at the eight hour time point (or twenty four hour time pointin case of Loxoribine and its prodrugs) from TLR7 ligand treated andcontrol wells and are assayed for interferon-alpha production by ELISA.Supernatants from compound-treated cells and a no-drug control werediluted at 1:10, 1:100, and 1:1000 in RPMI media and applied to a96-well plate of Huh7 hepatocyte cells containing the luciferasereporter replicon. Cells were incubated for 48 hours at 37° C. in atissue culture incubator.

After the incubation period, the 96-well plates are washed 2× with PBSand are lysed with passive lysis buffer (Promega). Plates are shaken atroom temperature for 20 minutes and standard luciferase assay reagent(Promega) is added to each well by injection and the plate is read on anLmax luminometer (Molecular Devices). The raw relative light units areconverted to a percent inhibition that is compared to the no-drugcontrol wells to determine the level of inhibition observed in thereplicon assay. The estimated maximal concentration of interferonsrequired to inhibit HCV replicon replication was determined to be at a1:10 dilution of supernatant of PBMC-stimulated cells which fell withinour test range of the dilution series. For all TLR7 agonists tested,100% inhibition was observed on the luciferase reporter replicon systemat the 1:10 dilution.

The data presented in Tables 3-8 represents the inhibition of the HCVreplicon system by the supernatant collected after exposure of PBMCcells to the compound at an initial concentration for the incubationtime indicated and diluted as specified in the first column (“PBMCexposed to compound”). A supernatant collected from PBMC cellsnon-exposed to the compound and diluted as specified in the first columnwas used as a control (“Blank supernatant”). The PBMC cells wereisolated from a single blood donor as specified.

TABLE 3 Antiviral Effect of Isatoribine in the in vitro HCV RepliconBioassay No. 1 Incubation time: 8 hours Initial concentration: 100 μMBlood donor number: FL72035 HCV replicon inhibition, % Dilution of PBMCexposed supernatant Blank PBMC to compound 1:100 0 100 1:1000 0 94 No. 2Incubation time: 8 hours Initial concentration: 100 μM Blood donornumber: FL75287 HCV replicon inhibition, % Dilution of PBMC exposedsupernatant Blank PBMC to compound 1:10 0 100 1:100 0 87 1:1000 0 6 No.3 Incubation time: 24 hours Initial concentration: 100 μM Blood donornumber: FL75864 HCV replicon inhibition, % Dilution of PBMC exposedsupernatant Blank PBMC to compound 1:10 0 100 1:100 23 99 1:1000 0 64

TABLE 4 Antiviral Effect of Loxoribine in the in vitro HCV RepliconBioassay No. 1 Incubation time: 24 hours Initial concentration: 100 μMBlood donor number: FL75864 HCV replicon inhibition, % Dilution of PBMCexposed supernatant Blank PBMC to compound 1:10 0 100 1:100 23 74 1:10000 17

TABLE 5 Antiviral Effect of Imiquimod in the in vitro HCV RepliconBioassay No. 1 Incubation time: 8 hours Initial concentration: 3.2 μMBlood donor number: FL75287 HCV replicon inhibition, % Dilution of PBMCexposed supernatant Blank PBMC to compound 1:10 0 100 1:100 0 100 1:10000 89 No. 2 Incubation time: 8 hours Initial concentration: 3.2 μM Blooddonor number: FL75287 HCV replicon inhibition, % Dilution of PBMCexposed supernatant Blank PBMC to compound 1:10 3 100 1:100 13 75 1:10003 1

TABLE 6 Antiviral Effect of Resiquimod in the in vitro HCV RepliconBioassay No. 1 Incubation time: 8 hours Initial concentration: 10 μMBlood donor number: FL75287 HCV replicon inhibition, % Dilution of PBMCexposed supernatant Blank PBMC to compound 1:10 0 100 1:100 0 98 1:10000 21 No. 2 Incubation time: 8 hours Initial concentration: 10 μM Blooddonor number: FL75287 HCV replicon inhibition, % Dilution of PBMCexposed supernatant Blank PBMC to compound 1:10 3 100 1:100 13 88 1:10003 6

TABLE 7 Antiviral Effect of Bropirimine in the in vitro HCV RepliconBioassay No. 1 Incubation time: 8 hours Initial concentration: 100 μMBlood donor number: FL72035 HCV replicon inhibition, % Dilution of PBMCexposed supernatant Blank PBMC to compound 1:10 0 100 1:100 0 95 1:10000 0 No. 2 Incubation time: 8 hours Initial concentration: 100 μM Blooddonor number: FL72036 HCV replicon inhibition, % Dilution of PBMCexposed supernatant Blank PBMC to compound 1:10 0 100 1:100 8 95 1:10000 33

TABLE 8 Antiviral Effect of Adenine Derivative in the in vitro HCVReplicon Bioassay No. 1 Incubation time: 8 hours Initial concentration:0.1 μM Blood donor number: FL76418 Form of the compound: a TFA salt HCVreplicon inhibition, % Dilution of PBMC exposed supernatant Blank PBMCto compound 1:10 0 100 1:100 3 73 1:1000 3 0 No. 2 Incubation time: 8hours Initial concentration: 0.1 μM Blood donor number: FL76418 Form ofthe compound: a TFA salt HCV replicon inhibition, % Dilution of PBMCexposed supernatant Blank PBMC to compound 1:10 0 100 1:100 3 64 1:10003 9

6.3 Preparation of TLR7 Ligand Prodrugs

Compounds of the invention can be synthesized using the methodologydescribed in Schemes 1-18 above. Unless otherwise indicated alltemperatures are set forth in degrees Celsius and all parts andpercentages are by weight. Reagents are purchased from commercialsuppliers such as Aldrich Chemical Company or Lancaster Synthesis Ltd.and are used without further purification unless otherwise indicated.Tetrahydrofuran (THF) and N,N-dimethylforamide (DMF) are purchased fromAldrich in Sure Seal bottles and used as received. Unless otherwiseindicated, the following solvents and reagents are distilled under ablanket of dry nitrogen. THF and Et₂O are distilled from Na-benzophenoneketyl; CH₂Cl₂ (DCM), diisopropylamine, pyridine and Et₃N are distilledfrom CaH₂; MeCN is distilled first from P₂O₅, then from CaH₂; MeOH isdistilled from Mg; PhMe, EtOAc and i-PrOAc are distilled from CaH₂; TFAAwas purified via simple atmospheric distillation under dry argon.

The reactions set forth are done generally under a positive pressure ofargon at an ambient temperature (unless otherwise stated) in anhydroussolvents, and the reaction flasks are fitted with rubber septa for theintroduction of substrates and reagents via syringe. Glassware is ovendried and/or heat dried. The reactions are assayed by TLC and terminatedas judged by the consumption of starting material. Analytical thin layerchromatography (TLC) is performed on aluminum-backed silica gel 60 F2540.2 mm plates (EM Science), and visualized with UV light (254 nm)followed by heating with commercial ethanolic phosphomolybdic acid.Preparative thin layer chromatography (TLC) is performed onaluminum-backed silica gel 60 F254 1.0 mm plates (EM Science) andvisualized with UV light (254 nm). HPLC is performed on a WatersMicromass ZQ system consisting of a model 2525 binary gradient pump withan Alltech model 800 ELSD detector and a Waters model 996 photodiodearray detector.

Work-ups are typically done by doubling the reaction volume with thereaction solvent or extraction solvent and then washing with theindicated aqueous solutions using 25% by volume of the extraction volumeunless otherwise indicated. Product solutions are dried over anhydrousNa₂SO₄ and/or Mg₂SO₄ prior to filtration and evaporation of the solventsunder reduced pressure on a rotary evaporator and noted as solventsremoved in vacuo. Column chromatography is completed under positivepressure using 230-400 mesh silica gel or 50-200 mesh neutral alumina.Hydrogenolysis is done at the pressure indicated in the examples or atambient pressure.

¹H-NMR spectra is recorded on a Varian Mercury-VX400 instrumentoperating at 400 MHz and ¹³C-NMR spectra are recorded operating at 75MHz. NMR spectra are obtained as CDCl₃ solutions (reported in ppm),using chloroform as the reference standard (7.27 ppm and 77.00 ppm),CD₃OD (3.4 and 4.8 ppm and 49.3 ppm), DMSO-d₆, or internallytetramethylsilane (0.00 ppm) when appropriate. Other NMR solvents areused as needed. When peak multiplicities are reported, the followingabbreviations are used: s (singlet), d (doublet), t (triplet), q(quartet), m (multiplet), br (broadened), dd (doublet of doublets), dt(doublet of triplets). Coupling constants, when given, are reported inHertz (Hz).

Infrared (IR) spectra are recorded on a Thermo Nicolet Avatar 370 FT-IRas neat oils or solids, and when given are reported in wave numbers(cm⁻¹). Mass spectra reported (+)-ES Thermo Finnegan LCQ LC/MS conductedby the Analytical Chemistry Department at Anadys Pharmaceuticals, Inc.Elemental analyses are conducted by the Atlantic Microlab, Inc. inNorcross, Ga. or by NuMega, in San Diego, Calif. Melting points (mp) aredetermined on an open capillary apparatus, and are uncorrected.

The described synthetic pathways and experimental procedures utilizemany common chemical abbreviations, THF (tetrahydrofuran), DMF(N,N-dimethylformamide), EtOAc (ethyl acetate), DMSO (dimethylsulfoxide), DMAP (4-dimethylaminopyridine), DBU(1,8-diazacyclo[5.4.0]undec-7-ene), DCM(4-(dicyanomethylene)-2-methyl-6-(4-dimethylamino-styryl)-4-H-pyran),MCPBA (3-chloroperoxybenzoic acid), EDC(1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride), HATU(O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyluroniumhexafluorophosphate), HOBT (1-hydroxybenzotriazole hydrate), TFAA(trifluoroacetic anhydride), pyBOP(benzotriazol-1-yloxy)tripyrrolidinophosphonium hexafluorophosphate),DIEA (diisopropylethylamine), and the like.

Example 1 7-Allyl-2-amino-9-β-D-ribofuranosyl-7,9-dihydro-purin-8-one(43)

Step 1: Preparation of7-Allyl-2-amino-9-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-7,9-dihydro-1H-purine-6,8-dione(40)

A heterogeneous mixture of7-allyl-2-amino-9-β-D-ribofuranosyl-7,9-dihydro-1H-purine-6,8-dione 17(1.00 g, 2.95 mmol, prepared according to Reitz et al., JMC, 37,3561-3578 (1994)), DMAP (0.036 mg, 0.29 mmol) and NEt₃ (2.05 mL, 14.74mmol) was stirred in dry acetonitrile (25 mL). Acetic anhydride (0.862mL, 9.13 mmol) was added slowly to the suspension and the reactionmixture was stirred at ambient temperature for 16 h. The solvent wasremoved under vacuum and the residue dissolved in dichloromethane (DCM).The organic phase was then washed with saturated aqueous sodiumbicarbonate (NaHCO₃), brine and thereafter dried with anhydrousmagnesium sulfate (MgSO₄). The solvent was concentrated under vacuum anddried at room temperature under high vacuum to give 1.33 g of 40 (97%)as a pale yellow solid: ¹H NMR (400 MHz, CDCl₃) δ 6.12 (t, J=6.0 Hz,1H), 6.01 (d, J=3.6 Hz, 1H), 5.89 (m, 1H), 5.82 (t, J=6.0 Hz, 1H), 5.39(br s, 2H), 5.21 (m, 2H), 4.58 (br s, 2H), 4.51 (m, 1H), 4.32 (m, 2H),2.16 (s, 3H), 2.15 (s, 3H), 2.10 (s, 3H); MS (+)-ES [M+H]⁺ 466.2 m/z.

Step 2: Preparation of7-Allyl-2-amino-6-chloro-9-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-7,9-dihydro-purin-8-one(41)

Compound 40 (0.65 g, 1.39 mmol) was dissolved in phosphorus oxychloride(10 mL) and heated to 75° C. for 16 h. The reaction mixture wasconcentrated under vacuum and the crude product dissolved in DCM. Themixture was then washed with NaHCO₃ solution, brine, dried (MgSO4) andfiltered. The filtrate was concentrated under vacuum and purified byflash chromatography using 10 to 50% gradient of ethyl acetate inhexanes. Removal of the solvent afforded 280 mg (41%) of the desiredproduct 41: ¹H NMR (400 MHz, CDCl₃) δ 6.04 (d, J=4.0 Hz, 1H), 6.03 (t,J=5.6 Hz, 1H), 5.87 (m, 1H), 5.86 (t, J=5.6 Hz, 1H), 5.18 (m, 4H), 4.59(d, J=8.0 Hz, 2H), 4.45 (d, J=7.6 Hz, 1H), 4.31 (m, 2H), 2.10 (s, 3H),2.08 (s, 3H), 2.04 (s, 3H); MS (+)-ES [M+H]⁺ 484.2 m/z.

Step 3: Preparation of7-Allyl-2-amino-9-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-7,9-dihydro-purin-8-one(42)

Compound 41 (0.27 g, 0.56 mmol) was dissolved in acetic acid and Zn—Cucouple was added to the solution. The mixture was heated at 70° C. for18 h. The suspended particles were filtered off and the filtrateconcentrated under vacuum. The residue was purified by flashchromatography using 10% to 100% gradient of ethyl acetate in hexanes.The solvent was removed to give 150 mg (60%) of 42 as off-white solid:¹H NMR (400 MHz, CDCl₃) δ 6.05 (t, J=4.0 Hz, 1H), 6.03 (d, J=4.0 Hz,1H), 5.87 (t, J=6.0 Hz, 1H), 5.83 (m, 1H), 5.48 (br s, 2H), 5.33 (s,1H), 5.29 (d, J=5.6 Hz, 1H), 4.49 (d, J=3.2 Hz, H), 4.46 (d, J=3.2 Hz,1H), 4.41 (d, J=5.6 Hz, 2H), 4.27 (m, 2H), 2.12 (s, 3H), 2.10 (s, 3H),2.05 (s, 3H); MS (+)-ES [M+H]⁺ 450.0 m/z.

Step 4: Preparation of7-Allyl-2-amino-9-β-D-ribofuranosyl-7,9-dihydro-purin-8-one (43)

To a solution of 42 (0.13 g, 0.29 mmol) in methanol (4 mL) was addedsolid K₂CO₃ (0.024 g, 0.17 mmol) and the reaction stirred at ambienttemperature for 18 h. To the cloudy mixture was added Amberlite CG-50(0.5 g) and stirred till neutral and filtered. The filtrate wasconcentrated to give an off-white solid, which was washed with water anddried under high vacuum to give 93.5 mg of pure 43 in quantitative yieldas an off white solid: ¹H NMR (400 MHz, d₆-DMSO) δ 7.88 (s, 1H), 6.33(br s, 2H), 5.85 (m, 1H), 5.66 (d, J=6.0 Hz, 1H), 5.30 (d, J=5.6 Hz,1H), 5.20 (s, 1H), 5.16 (d, J=8.4 Hz, 1H), 5.01 (d, J=4.8 Hz, H), 4.89(q, J=5.6 Hz, 1H), 4.75 (br s, 1H), 4.35 (d, J=5.2 Hz, 2H), 4.10 (t,J=8.4 Hz, 1) 3.80 (q, J=3.6 Hz, 1H), 3.57 (m, 1H), 3.44 (m, 1H). MS(+)-ES [M+H]⁺ 324.1 m/z.

Example 27-Allyl-2-amino-6-ethoxy-9-β-D-ribofuranosyl-7,9-dihydro-purin-8-one(45)

Step 1: Preparation of7-Allyl-2-amino-6-ethoxy-9-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-7,9-dihydro-purin-8-one(44)

To a solution of 40 (0.30 g, 0.64 mmol) in dry THF (15 mL) was addedpolymer-supported triphenylphosphine (0.89 g, 1.93 mmol) and EtOH (0.11mL, 1.93 mmol) at room temperature. To the stirring mixture was addeddiethyl azodicarboxylate (0.12 mL, 0.77 mmol) and stirring continued for18 h. The spent polymer support was filtered off and the solvent removedunder vacuum. The residue was then purified by flash chromatographyusing 10 to 50% gradient of ethyl acetate in hexanes. Removal of thesolvent afforded 85 mg (26%) of the desired product 6 as a clear oil: ¹HNMR (400 MHz, CDCl₃) δ 6.07 (d, J=4.0 Hz, 1H), 6.06 (d, J=4.0 Hz, 1H),6.01 (d, J=3.6 Hz, 1H), 5.96 (t, J=6.0 Hz, 1H), 5.87 (m, 1H), 5.14 (d,J=2.2 Hz, 1H), 5.15 (m, 1H), 4.80 (br s, 2H), 4.46 (m, 4H), 4.37 (q,J=7.2 Hz, 2H), 4.29 (m, 2H), 2.09 (s, 3H), 2.08 (s, 3H), 2.04 (s, 3H),1.35 (t, J=7.6 Hz, 3H); MS (+)-ES [M+H]⁺ 494.1 m/z.

Step 2: Preparation of7-Allyl-2-amino-6-ethoxy-9-β-D-ribofuranosyl-7,9-dihydro-purin-8-one(45)

To a solution of 44 (0.084 g, 0.17 mmol) in methanol (4 mL) was addedsolid K₂CO₃ (0.014 g, 0.17 mmol) and the reaction stirred at ambienttemperature for 1 h. To the cloudy mixture was added Amberlite CG-50(0.5 g) and stirred till neutral and filtered. The filtrate wasconcentrated and purified by flash chromatography using 100% DCM to 10%of methanol in DCM. Removal of the solvent afforded 62 mg of 7 (99%) asa clear oil: ¹H NMR (400 MHz, CDCl₃) δ 5.97 (d, J=8.0 Hz, 1H), 5.93 (m,1H), 5.25 (d, J=32.4, Hz, H), 5.21 (s, 1H), 5.02 (t, J=8.0 Hz, 1H), 4.62(br s, 2H), 4.47 (d, J=5.6 Hz, 2H), 4.25-4.45 (m, 3H), 4.21 (q, J=6.8Hz, 2H), 3.77 (ABq, Δυ_(AB)=0.14, J_(AB)=12.4 Hz, 2H), 1.37 (t, J=6.8Hz, 3H), 1.27 (t, 7.6, 2H); MS (+)-ES [M+H]⁺ 368.0 m/z.

Example 3 5-Bromo-4-ethoxy-6-phenyl-pyrimidin-2-ylamine (37)

Step 1: Preparation of 5-Bromo-4-ethoxy-6-phenyl-pyrimidin-2-ylamine(37)

In a manner similar to step 2 of Example 2 was prepared the titlecompound as a white solid from2-amino-5-bromo-6-phenyl-3H-pyrimidin-4-one 35 (Wierenga, et al., JMC,23, 239-240 (1980)) in 13% yield: ¹H NMR (400 MHz, CDCl₃) δ 7.61 (m,2H0, 7.42 (m, 3H), 5.15 (br s, 2H), 4.23 (q, J=7.2 Hz, 2H), 1.44 (t, 6.8Hz, 3H); MS (+)-ES [M]⁺294.1 [M+2]⁺296.0 m/z. Elemental analysis forC₁₂H₁₂BrN₃O: calc'd: C, 49.00; H, 4.11; N, 14.29. Found: C, 48.94; H,4.18; N, 14.01.

Example 44-(2-Amino-5-bromo-6-phenyl-pyrimidin-4-yloxymethyl)-5-methyl-[1,3]dioxol-2-one(46)

Step 1: Preparation of4-(2-Amino-5-bromo-6-phenyl-pyrimidin-4-yloxymethyl)-5-methyl-[1,3]dioxol-2-one(46)

In a manner similar to step 2 of Example 2 was prepared the titlecompound as a white solid from2-Amino-5-bromo-6-phenyl-3H-pyrimidin-4-one 35 in 4% yield: ¹H NMR (400MHz, CDCl₃) δ 7.62 (m, 2H), 7.45 (m, 3H), 5.18 (s, 2H), 5.07 (s, 2H),2.26 (s, H); MS (+)-ES [M]⁺ 378.2 [M+2]⁺ 380.1 m/z. Elemental analysisfor C₁₅H₁₂BrN₃O₄: calc'd: C, 47.64; H, 3.20; N, 11.11. Found: C, 46.98;H, 3.23; N, 10.70.

Example 5 5-Bromo-4-phenyl-pyrimidin-2-ylamine (48)

Step 1: Preparation of 4-Phenyl-pyrimidin-2-ylamine (47)

To a solution of bromobenzene (4.43 mL, 42.06 mmol) in dry THF (100 mL)at −78° C. was added BuLi (394 mL, 63.08 mmol) and the mixture left tostir at −78° C. for 2 h. To this was added 2-aminopyrimidine (2.0 g,21.03 mmol) in hot toluene (80 mL) over a 15 minutes period. The mixturewas refluxed for 16 h and allowed to cool to room temperature andcarefully quenched with aqueous NaHCO₃. The mixture was filtered and thefiltrate concentrated under vacuum. The residue was then dissolved inDCM and washed with aqueous NaHCO₃, brine and dried (MgSO4). The solventwas removed to afford 350 mg of 47 (10%) as a pale yellow solid: ¹H NMR(400 MHz, CDCl₃) δ 8.32 (d, J=4.8 Hz, 1H), 7.97 (m, 2H), 7.45 (m, 3H),7.02 (J=4.8 Hz, 1H). 5.27 (br s, 2H); MS (+)-ES [M+H]⁺ 172.2 m/z.

Step 2: Preparation of 5-Bromo-4-phenyl-pyrimidin-2-ylamine (48)

Compound 47 (0.30 g, 1.75 mmol) was dissolved in glacial acetic acid (15ml) and warmed to 45° C. Br₂ (0.09 mL, 1.75 mmol) was added slowly. Theresulting mixture was then allowed to stir at room temperature for 3 h.The solvent was removed under vacuum to a solid residue. This was thentransferred onto a filter funnel and washed with DCM, followed by water.The remaining solid was then dried under high vacuum for 16 h to give197 mg of 13 (45%) as a pale yellow solid: ¹H NMR (400 MHz, d₆-DMSO) δ8.40 (s, 1H), 7.61 (m, 2H), 7.45 (m, 3H), 6.96 (s, 2H); MS (+)-ES [M]⁺250.0 [M+2]⁺ 252.0 m/z. Elemental analysis for C₁₀H₈BrN₃: calc'd: C,48.02; H, 3.22; Br, 31.95; N, 16.80. Found: C, 47.91; H, 3.28; Br,32.15; N, 16.80.

Example 6 (5-Bromo-6-oxo-4-phenyl-1,6-dihydro-pyrimidin-2-yl)-carbamicacid ethyl ester (36)

Step 1: Preparation of(5-Bromo-6-oxo-4-phenyl-1,6-dihydro-pyrimidin-2-yl)-carbamic acid ethylester (36)

To a solution of 35 (0.25 g, 0.94 mmol) in DMF (8 mL) was added NEt₃(0.14 mL, 0.99 mmol) and diethyl pyrocarbonate (0.27 mL, 1.89 mmol). Thereaction mixture was maintained at 65° C. for 20 h. The solvent wasremoved and the residue treated with DCM. The resulting mixture wasfiltered to remove the remaining starting material 35 and the filtratewashed with aqueous NaHCO₃, brine and dried (MgSO₄). The filtrate wasconcentrated and purified by HPLC (Thomson ODS-A 100A 5μ 150×21.2 mmcolumn; flow rate=30 mL/min; CH₃CN with 0.05% TFA (A), Water with 0.05%TFA (B); Make up pump flow=0.9 mL/min; Make up pump mobile phase; MeOHwith 0.05% TFA using a gradient system as follows: t=0; 15% A, 85% B;t=3.0 min; 15% A, 85% B; t=9.5 min; 70% A, 30% B; t=10.0 min; 100% A, 0%B; t=12.0 min; 100% A, 0% B; t=12.5 min; 15% A, 85% B; t=15.0 min; 15%A, 85% B.) to afford 54 mgs of 36 (17%) as a clear oil: ¹H NMR (400 MHz,CDCl₃) δ 7.66 (m, 1H), 7.44 (m, 3H), 4.26 (q, J=7.6 Hz, 2H), 1.32 t,J=6.8 Hz, 3H); MS (+)-ES [M]⁺ 338.1 [M+2]⁺ 340.0 m/z. Elemental analysisfor C₁₃H₁₂BrN₃O₃: calc'd: C, 46.17; H, 3.58; N, 12.43. Found: C, 46.43;H, 3.74; N, 11.95.

Example 7 (5-Bromo-6-oxo-4-phenyl-1,6-dihydro-pyrimidin-2-yl)-carbamicacid pentyl ester (49)

Step 1: Preparation of(5-Bromo-6-oxo-4-phenyl-1,6-dihydro-pyrimidin-2-yl)-carbamic acid pentylester (49)

In a manner similar to step 1 of Example 6 the title compound wasprepared from 35 and dipentyl pyrocarbonate as a clear oil in 9% yieldafter HPLC purification (Thomson ODS-A 100A 5μ 150×21.2 mm column; flowrate=30 mL/min; CH₃CN with 0.05% TFA (A), Water with 0.05% TFA (B); Makeup pump flow=0.9 mL/min; Make up pump mobile phase; MeOH with 0.05% TFAusing a gradient system as follows: t=0; 35% A, 65% B; t=3.0 min; 35% A,65% B; t=10 min; 100% A, 0% B; t=12.0 min; 100% A, 0% B; t=12.5 min; 35%A, 65% B; t=15.0 min; 35% A, 65% B.). ¹H NMR (400 MHz, CDCl₃) δ 7.69 (brs, 1H), 7.67 (m, 2H), 7.43 (d, J=2.0 Hz, 3H), 4.17 (t, J=7.2 Hz, 2H),1.64 (t, J=6.8 Hz, 2H), 1.34 (m, 4H), 0.92 (t, J=6.4 Hz, 3H); MS (+)-ES[M]⁺ 380.1 [M+2]⁺ 382.1 m/z.

Example 8 (1-Isobutyl-1H-imidazo[4,5-c]quinolin-4-yl)-carbamic acidpentyl ester (34)

Step 1: Preparation of(1-Isobutyl-1H-imidazo[4,5-c]quinolin-4-yl)-carbamic acid pentyl ester(34)

To a suspension of 1-Isobutyl-1H-imidazo[4,5-c]quinolin-4-ylamine 31(0.15 g, 0.62 mmol, prepared according to the procedure given inWO94/17043) in CHCl₃ (5 mL) was added NEt₃ (0.09 mL, 0.65 mmol) anddipentyl pyrocarbonate (0.231 g, 0.94 mmol). The mixture was stirred at40° C. for 60 h. The reaction mixture was washed with aqueous NaHCO₃,brine and dried over MgSO₄. The filtrate was concentrated and purifiedby flash chromatography using a 10% to 70% gradient of ethyl acetate inhexanes to give 50.5 mg of 34 (23%) as a white solid: ¹H NMR (400 MHz,CDCl₃) δ 8.31 (br s, 1H), 8.15 (t, J=8.0 Hz, 2H), 7.85 (t, J=7.2 Hz,1H), 7.77 (t, J=8.0 Hz, 1H), 4.43 (d, J=7.6 Hz, 2H), 4.36 (t, J=7.2 Hz,2H), 2.31 (m, 1H), 1.75 (t, J=6.8 Hz, 2H), 1.36 (m, 4H), 1.06 (d, J=6.4Hz, 6H), 0.89 (t, J=6.8 Hz, 2H); MS (+)-ES [M+H]⁺ 355.3 m/z.

Example 9 (1-Isobutyl-1H-imidazo[4,5-c]quinolin-4-yl)-carbamic acidethyl ester (50)

Step 1: Preparation of(1-Isobutyl-1H-imidazo[4,5-c]quinolin-4-yl)-carbamic acid ethyl ester(50)

In a manner similar to step 1 of Example 8 was prepared the titlecompound as a white solid from 31 and diethyl pyrocarbonate in 67% yieldas a white solid: ¹H NMR (400 MHz, CDCl₃) δ 9.32 (br s, 2H), 8.2 (d,J=8.0 Hz, 2H) 8.12 (d, J=8.0 Hz, 1H), 7.83 (t, J=7.2 Hz, 1H), 7.74 (t,J=8.0 Hz, 1H) 4.43 (m, 4H), 2.35 (m, 1H), 1.39 (t, J=7.2 Hz, 3H), 1.08(d, J=6.4 Hz, 6H); MS (+)-ES [M+H]⁺ 313.2 m/z.

Example 10 Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester ethyl ester(51)

Step 1: Preparation of Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester ethyl ester(51)

6-Amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-ol, 29 (11.75 mg, 0.027mmol, prepared according to the procedure described by Kurimota, et al.,Bioorg. Med. Chem., 12, 1091-109 (2004) was suspended in CH₂Cl₂ (0.6 mL)and cooled to 0° C. DIEA (11.96 μL, 0.068 mmol) and ethyl chloroformate(3.86 mg, 0.036 mmol, added as a 10% by volume solution indichloromethane) were then added to the suspension. The reaction mixturewas stirred at 0° C. for 10 minutes then allowed to warm to roomtemperature for 15 minutes. TLC of the reaction mixture shows thatstarting material remained. The reaction mixture was heated to 35° C.,DMAP (cat.), methanol (60 μL portions) was added to dissolve 29, andadditional aliquots of ethyl chloroformate (3.86 mg, 0.036 mmol, addedas a 10% by volume solution in dichloromethane) were added until thereactions was complete. The crude mixture was purified by flashchromatography using a 0 to 100% gradient of ethyl acetate in hexane.The desired peaks were collected and concentrated in-vacuo to yield 8.5mg (80%) of compound 51 as a white solid: ¹H NMR (400 MHz, CDCl₃) δ 7.45(d, J=Hz, 2H), 7.27 (m, 3H), 4.98 (s, 2H), 4.46 (m, 4H), 3.74 (m, 2H),3.42 (s, 2H), 1.46 (t, 3H); MS [M+H]+ m/z 388.3.

Examples 11-20 were prepared from6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-ol, 29 and theappropriate chloroformate according to the procedure described inExample 10.

Example 11 Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester propyl ester(52)

86% yield as a white solid: ¹H NMR (400 MHz, CDCl₃) δ 7.45 (d, J=6.4 Hz,2H), 7.27 (m, 3H), 4.98 (s, 2H), 4.46 (m, 4H), 3.74 (t, J=5.2 Hz, 2H),3.42 (s, 3H), 1.46 (t, J=7.6 Hz, 3H); MS [M+H]⁺ m/z 402.2.

Example 12 Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester isobutyl ester(53)

92% yield as a white solid: ¹H NMR (400 MHz, CDCl₃) δ 7.45 (d, J=6.4 Hz2H), 7.27 (m, 3H), 4.99 (s, 2H), 4.45 (m, 2H), 4.17 (d, J=7.4 Hz, 2H),3.73 (t, J=4.8 Hz, 2H), 3.4 (s, 3H), 2.15 (m, 1H), 1.06 (d, J=6.8 Hz,6H); MS [M+H]+ m/z 416.3.

Example 13 Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester pentyl ester(54)

92% yield as a white solid: ¹H NMR (400 MHz, CDCl₃) δ 7.45 (d, J=6.4 Hz,2H), 7.27 (m, 3H), 4.99 (s, 2H), 4.45 (t, J=4.8 Hz, 2H), 4.39 (t, J=7.2Hz, 2H), 3.73 (t, J=5.2 Hz, 2H), 3.4 (s, 3H), 2.15 (m, 1H), 1.82 (m,2H), 1.40 (m, 4H), 0.93 (t, J=6.8 Hz, 3H); MS [M+H]+ m/z 430.2.

Example 14 Carbonic acid allyl ester6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester (55)

93% yield as a white solid: ¹H NMR (400 MHz, CDCl₃) δ 7.46 (d, J=6.0 Hz,2H), 7.25 (m, 3H), 6.0 (m, 1H), 5.5 (m, 1H), 5.35 (m, 1H), 4.99 (s, 2H),4.89 (d, J=2.4 Hz, 2H), 4.46 (t, J=4.8 Hz, 2H), 3.74 (d, J=5.2 Hz, 2H),3.42 (s, 3H); MS [M+H]+ m/z 400.2.

Example 15 Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester 4-chloro-butylester (56)

98% yield as a white solid: 1H ¹H NMR (400 MHz, CDCl₃) δ 7.44 (d, J=6.0Hz, 2H), 7.25 (m, 3H), 4.98 (s, 2H), 4.45 (m, 4H), 3.63 (t, J=5.2 Hz,2H), 3.42 (s, 3H), 1.99 (m, 4H); MS [M+H]+ m/z 450.2.

Example 16 Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester butyl ester(57)

100% yield as a white solid: ¹H NMR (400 MHz, CDCl₃) δ 7.45 (d, J=6.0Hz, 2H), 7.27 (m, 3H), 4.99 (s, 2H), 4.46 (m, 2H), 4.41 (t, J=4.4 Hz,2H), 3.73 (t, J=7.2 Hz, 2H), 3.42 (s, 3H), 1.79 (m, 2H), 1.48 (m, 2H),0.96 (t, J=7.6 Hz, 3H); MS [M+H]+ m/z 416.2.

Example 17 Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester phenyl ester(58)

100% yield as a white solid: ¹H NMR (400 MHz, CDCl₃) δ 7.52 (d, J=6.8Hz, 2H), 7.41 (m, 2H), 7.30 (m, 3H), 7.25 (m, 3H), 4.99 (s, 2H), 4.47(t, J=4.8 Hz, 2H), 3.75 (t, J=4.8 Hz, 2H), 3.43 (s, 3H); MS [M+H]+ m/z436.2.

Example 18 Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester2,2-dimethyl-propyl ester (59)

100% yield as a white solid: ¹H NMR (400 MHz, CDCl₃) δ 7.43 (d, 2H),7.25 (m, 3H), 4.99 (s, 2H), 4.47 (t, 2H), 4.08 (s, 2H), 3.75 (t, 2H),3.42 (s, 3H), 1.07 (s, 9H); MS [M+H]+ m/z 430.2.

Example 19 Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester heptyl ester(60)

100% yield as a white solid: ¹H NMR (400 MHz, CDCl₃) δ 7.45 (d, J=6.0Hz, 2H), 7.27 (m, 3H), 4.99 (s, 2H), 4.46 (t, J=5.2 Hz, 2H), 4.39 (t,J=7.2 Hz, 2H), 3.74 (t, J=5.2 Hz, 2H), 3.42 (s, 3H), 1.8 (m, 2H), 1.4(m, 2H), 1.3 (m, 6H) 0.87 (t, J=7.2 Hz, 3H); MS [M+H]+ m/z 458.3.

Example 20 Carbonic acid6-amino-9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-8-yl ester hexyl ester(30)

74% yield as a white solid: ¹H NMR (400 MHz, CDCl₃) δ 7.45 (d, J=5.6 Hz,2H), 7.27 (m, 3H), 4.98 (s, 2H), 4.45 (t, J=4.8 Hz, 2H), 4.41 (t, J=6.8Hz, 2H), 3.73 (t, J=4.4 Hz, 2H), 3.42 (s, 3H), 1.81 (m, 2H), 1.34 (m,2H), 1.31 (m, 2H), 1.26 (m, 2H), 0.89 (t, J=2 Hz, 3H); MS [M+H]+ m/z444.4.

Examples 22 and 23 were prepared from9-benzyl-2-(2-methoxy-ethoxy)-9H-purin-6-ylamine, 62, via9-benzyl-8-bromo-2-(2-methoxy-ethoxy)-9H-purin-6-ylamine, 63 and sodiumethoxide or methoxide respectively according to the procedures ofKurimota et al., Bioorg. Med. Chem., 12, 1091-1099 (2004).

Example 21 9-Benzyl-2-(2-methoxy-ethoxy)-9H-purin-6-ylamine (62)

100% yield as a brown solid: ¹H NMR (400 MHz, CDCl₃) δ 7.59 (s, 1H),7.27 (m, 5H), 5.83 (s, 2H), 5.26 (s, 2H), 4.49 (t, J=4.8 Hz, 2H), 3.75(t, J=5.2 Hz, 2H), 3.43 (s, 3H); MS [M+H]⁺ m/z 300.2.

Example 22 9-Benzyl-8-ethoxy-2-(2-methoxy-ethoxy)-9H-purin-6-ylamine(64)

91% yield as a brown solid: ¹H NMR (400 MHz, d₆-DMSO) δ 7.24 (m, 2H),7.24 (m, 3H), 5.00 (s, 2H), 4.42 (m, 2H), 4.27 (t, J=4.8 Hz, 2H), 3.58(t, J=4.8 Hz, 2H), 3.26 (s, 3H), 1.32 (t, J=7.2 Hz, 3H); MS [M+H]⁺ m/z344.1.

Example 23 9-Benzyl-8-methoxy-2-(2-methoxy-ethoxy)-9H-purin-6-ylamine(65)

91% yield as a brown solid: ¹H NMR (400 MHz, d₆-DMSO) δ 7.28 (m, 2H),7.22 (m, 3H), 6.86 (s, 2H), 5.01 (s, 2H), 4.26 (t, J=4.4 Hz, 2H), 4.02(s, 3H), 3.58 (t, J=4.8 Hz, 2H), 3.25 (s, 3H); MS [M+H]⁺ m/z 330.2.

Example 247-Allyl-2-Amino-9-(5′-O-L-valinyl-β-D-ribofuranosyl)-7,9-dihydro-1H-purine-6,8-dione(68)

Step 1: Preparation of 7-Allyl-2-amino-9-(2′,3′-O-isopropylidene-β-D-ribofuranosyl)-7,9-dihydro-1H-purine-6,8-dione(66)

Compound 17 (0.17 g, 0.49 mmol) was dissolved in DMF (4.0 mL) andacetone (3.0 mL) was added to the solution. To the mixture was added2,2-dimethoxypropane (0.18 mL, 1.47 mmol) and MeSO₃H (0.02 mL, 0.05mmol). The reaction mixture was stirred at ambient temperature for 20 hand quenched with saturated aqueous NaHCO₃. The aqueous phase was thenextracted (4×) with CH₂Cl₂. The combined organic phase was dried(MgSO₄), filtered and concentrated under vacuum to afford 130 mg of 66in 70% yield as a white solid: ¹H NMR (400 MHz, CD₃OD) δ 5.97 (d, J=2.4Hz, 1H), 5.93 (m, 1H), 5.34 (dd, J=4.4, 2.0 Hz, 1H), 5.15 (m, 1H), 5.12(dd, J=7.6, 1.2 Hz, 1H), 4.98 (m, 1H), 4.52 (d, J=5.6, 2H), 4.16 (m,1H), 3.71 (m, 2H), 1.56 (s, 3H), 1.36 (s, 3H); MS (+)-ES [M+H]⁺ 380.0m/z.

Step 2: Preparation of7-Allyl-2-amino-9-(2′,3′-O-isopropylidene-5′-N-tert-butoxycarbonyl-L-valinyl)-β-D-ribofuranosyl)-7,9-dihydro-1H-purine-6,8-dione(67)

A mixture of 66 (0.13 g, 0.34 mmol), BOC-Valine (0.08 g, 0.36 mmol), EDC(0.07 g, 0.38 mmol), DMAP (0.05 g, 0.38 mmol) in THF (8.0 mL) andpyridine (0.8 mL) under N₂ atmosphere was stirred at ambient temperaturefor 16 h. The solvents were removed under vacuum and the residuedissolved in EtOAc. The organic phase was washed with saturated aqueousNaHCO₃, brine, dried (MgSO₄) and filtered. The filtrate was concentratedunder vacuum and the purified by flash chromatography using a 2% to 5%gradient of MeOH in CH₂Cl₂ to give 180 mg of 67 (91%) as pale yellowsolid: ¹H NMR (400 MHz, CDCl₃) δ 6.07 (s, 1H), 5.80 (m, 1H), 5.56 (br s,2H), 5.41 (d, J=5.6 Hz, 1H), 5.15 (m, 3H), 4.97 (br s, 1H), 4.53 (br s,2H), 4.46 (m, 1H), 4.32 (m, 2H), 4.20 (m, 1H), 2.11 (m, 1H), 1.56 (s,3H), 1.44 (s, 9H), 1.36 (s, 3H), 0.93 (d, J=6.8 Hz, 3H), 0.84 (d, J=6.8Hz, 3H); MS (+)-ES [M]⁺ 578.9 m/z.

Step 3:7-Allyl-2-Amino-9-(5′-O-L-valinyl-β-D-ribofuranosyl)-7,9-dihydro-1H-purine-6,8-dione(68)

To a solution of 67 (0.18 g, 0.311 mmols) in MeOH (10 mL) was added AcCl(0.86 mL, 12.07 mmol) under N₂ atmosphere. The reaction mixture was leftto stir at ambient temperature for 18 h and thereafter carefullyneutralized with saturated aqueous NaHCO₃. To the mixture was addedsilica gel and concentrated under vacuum. The residue was purified byflash chromatography using a 10% to 20% gradient of MeOH in CH₂Cl₂ togive 80 mg of 68 (59%) as a white solid: ¹H NMR (400 MHz, d₆-DMSO) δ6.72 (br s, 2H), 5.84 (m, 1H), 5.59 (d, J=4.8 Hz, 1H), 5.43 (d, J=5.6Hz, 1H), 5.15 (br s, 1H), 5.07 (d, J=12 Hz, 1H), 5.0 (d, J=18.8 Hz, 1H),4.77 (q, J=4.8 Hz, 1H), 4.36 (m, 3H), 4.26 (t, J=4.4 Hz, 1H), 4.20 (m,1H), 3.93 (m, 1H), 3.57 (br s, 1H), 2.01 (m, 1H), 0.86 (d, J=4.4 Hz,3H), 0.85 (d, J=5.2 Hz, 3H); MS (+)-ES [M+H]⁺ 439.1 m/z.

Example 257-Allyl-2-amino-9-β-D-ribofuranosyl-6-(5-methyl-2-oxo-[1,3]dioxol-4-ylmethoxy)-7,9-dihydro-purin-8-one(71)

Step 1: Preparation of7-Allyl-2-amino-9-(2′,3′,5′-tris-O-triethylsilanyl-β-D-ribofuranosyl)-7,9-dihydro-1H-purine-6,8-dione(69)

To a solution of 17 (0.46 g, 1.36 mmol) and imidazole (0.93 g, 13.64mol) in DMF (13 mL) was added chlorotriethylsilane (0.92 mL, 5.46 mmol)dropwise and stirred at ambient temperature for 2.5 h. The reactionmixture was treated with saturated aqueous NaHCO₃ and the resulting twophases separated. The aqueous phase was washed with diethyl ether (2×).The organic layers were combined and washed with water, dried (MgSO₄)and concentrated after filtration. The residue was purified by flashchromatography using a 2% to 10% gradient of MeOH in CH₂Cl₂ to give 830mg of 69 (89%) as pale yellow oil: ¹H NMR (400 MHz, CDCl₃) δ 5.92 (m,1H), 5.85 (d, J=6.8 Hz, H), 5.3 (m, 1H), 5.15-5.23 (m, 2H), 5.09 (br s,2H), 4.54 (d, J=4.4 Hz, 2H), 4.33 (m, 1H), 3.98 (m, 1H), 3.67-3.80 (m,2H), 0.85-1.02 (m, 26H), 0.48-0.71 (m, 19H): MS (+)-ES [M]⁺ 682.6 m/z.

Step 2: Preparation of7-Allyl-2-amino-9-(2′,3′,5′-tris-O-triethylsilanyl-β-D-ribofuranosyl)-6-(5-methyl-2-oxo-[1,3]dioxol-4-ylmethoxy)-7,9-dihydro-purin-8-one(70)

In a manner similar to Step 1 of Example 2, compound 70 was preparedfrom compound 69 and 4-hydroxymethyl-5-methyl-[1,3]dioxol-2-one(prepared according to the procedure of Alepegiani, Syn. Comm., 22(9),1277-82 (1992)) in 5% yield as a white solid after HPLC purification(Thomson ODS-A 100A 5u 50×21.2 mm column; flow rate=30 mL/min; CH₃CNwith 0.05% TFA (A), Water with 0.05% TFA (B); Make up pump flow=1.0mL/min; Make up pump mobile phase; MeOH with 0.05% TFA using a gradientsystem as follows: t=0; 50% A, 50% B; t=2.0 min; 50% A, 50% B; t=5.0min; 100% A, 0% B; t=9.5 min; 100% A, 0% B; t=10.0 min; 50% A, 50% B;t=13.0 min; 50% A, 50% B.); MS (+)-ES [M]⁺ 794.1 m/z.

Step 3: Preparation of7-Allyl-2-amino-9-β-D-ribofuranosyl-6-(5-methyl-2-oxo-[1,3]dioxol-4-ylmethoxy)-7,9-dihydro-purin-8-one(71)

To a solution of 70 (9.0 mg, 0.012 mmol) in MeOH (1.5 mL) was added3HF.NEt₃ (0.01 mL, 0.07 mmol) and stirred at ambient temperature for 16h. The solvent was removed under vacuum and the residue purified byflash chromatography. The desired product was eluted with 2% to 5%gradient of MeOH in CH₂Cl₂ to afford 3.26 mg of 71 (64%) as white solid:¹H NMR (400 MHz, CDCl₃) 5.96 (d, J=7.6 Hz, 1H), 5.85 (m, 1H), 5.17 (m,4H), 4.96 (t, J=7.2 Hz, 1H), 4.47 (d, J=6.0 Hz, 2H), 4.25 (J=5.2 Hz,1H), 4.24 (s, 1H), 3.81 (ABq, Δυ_(AB)=0.17, J_(AB)=11.6 Hz, 2H), 2.22(s, 3H): MS (+)-ES [M+H]⁺ 452.4 m/z.

Example 26(7-Allyl-2-amino-9-β-D-ribofuranosyl-8-oxo-8,9-dihydro-7H-purin-6-yloxymethyl)-methyl-carbamicacid ethyl ester (73)

Step 1: Preparation of(7-Allyl-2-amino-9-(2′,3′,5′-tris-O-triethylsilanyl-βD-ribofuranosyl)-8-oxo-8,9-dihydro-7H-purin-6-yloxymethyl)-methyl-carbamicacid ethyl ester (72)

In a manner similar to Step 1 of Example 2 compound 72 was prepared in4% yield from compound 69 and N-methyl-N-(hydroxymethyl)urethane(Kelper, JOC, 52, 1987, p. 453-455) as a white solid after HPLCpurification: ¹H NMR (400 MHz, CDCl₃) δ 5.94 (m, 1H), 5.82 (d, J=6.4 Hz,1H), 5.53 (br s, 1H), 5.23-5.29 (m, 2H), 5.15 (t, J=9.6 Hz, 1H), 4.57(d, J=5.2 Hz, 2H), 4.35 (br s, 1H), 4.21 (m, 2H), 3.96 (br s, 1H), 3.73(m, 2H), 3.06 (s, 3H), 1.30 (m, 4H), 0.87-1.01 (m, 2H), 0.57-0.68 (m,19H): MS (+)-ES [M+H]⁺ 797.7 m/z.

Step 2: Preparation of(7-Allyl-2-amino-9-β-D-ribofuranosyl-8-oxo-8,9-dihydro-7H-purin-6-yloxymethyl)-methyl-carbamicacid ethyl ester (73)

In a manner similar to Step 3 of Example 25 was prepared the titlecompound 73 in 64% as a white solid after HPLC purification (ThomsonODS-A 100A 5μ 50×21.2 mm column; flow rate=30 mL/min; CH₃CN with 0.05%TFA (A), Water with 0.05% TFA (B); Make up pump flow=1.0 mL/min; Make uppump mobile phase; MeOH with 0.05% TFA using a gradient system asfollows: t=0; 50% A, 50% B; t=2.0 min; 50% A, 50% B; t=5.0 min; 100% A,0% B; t=9.5 min; 100% A, 0% B; t=10.0 min; 50% A, 50% B; t=13.0 min; 50%A, 50% B.). ¹H NMR (400 MHz, CDCl₃) δ 5.92 (m, 1H), 5.92 (d, J=7.6 Hz,5H), 551 (m, 2H), 5.22 (d, J=15.6 Hz, 1H), 5.16 (d, J=9.2 Hz, 1H), 4.92(t, J=7.2 Hz, 1H), 4.57 (d, J=6.0, 2H), 4.40 (d, J=6.0, 1H), 4.21 (m,3H), 3.79 (ABq, Δυ_(AB)=0.178, J_(AB)=14.0 Hz, 2H), 3.06 (s, 3H), 1.31(t, J=7.2 Hz, 3H): MS (+)-ES [M]⁺ 455.4 m/z.

Example 275-Amino-3-(5′-O-L-valinyl-β-D-ribofuranosyl)thiazolo[4,5-d]pyrimidine-2,7-dioneDihydrochloride (24)

Step 1: Preparation of 5-Amino-3-(2′,3′-O-isopropylidene-β-D-ribofuranosyl)thiazolo[4,5-d]pyrimidine-2,7-dione (22)

To a heterogeneous mixture of 21 (5.37 g, 17.0 mmol, prepared accordingto the procedure given in U.S. Pat. No. 5,041,426 (Example 2), which isincorporated by reference in its entirety) in acetone (40 mL) containedin a 250 mL Morton flask was added successively 2,2-DMP (6.26 mL, 50.9mmol), DMSO (6.6 mL), and MeSO₃H (220 μL, 3.39 mmol) at roomtemperature. The reaction mixture was stirred vigorously, becominghomogeneous and golden yellow as the diol was consumed. TLC analysis(SiO₂, 10% MeOH—CHCl₃) indicated reaction completion after 6 h.Undissolved solids were removed via gravity filtration using flutedWhatman type 1 filter paper. This was followed by pouring of thefiltrate into 10 volumes of ice water (˜400 mL), resulting in immediateprecipitation of a white solid. After a brief period of stirring, NaHCO₃(285 mg, 3.39 mmol) dissolved in water (10 mL) was added to neutralizethe MeSO₃H. Vigorous stirring in the Morton reactor was continued for 15min, whereupon the mixture was filtered through a coarse scintered glassfunnel. The solid material was washed with ice water (100 mL), airdried, then dried further under high vacuum at 65° C., affording 5.36 g(88%) of the acetonide 22 as a white solid: mp 280-81° C.; ¹H (DMSO-d₆)δ 1.28 (s, 3H), 1.47 (s, 3H), 3.43-3.55 (m, 2H), 3.95-3.99 (m, 1H),4.77-4.80 (m, 1H), 4.88-4.91 (m, 1H), 5.24-5.26 (m, 1H), 5.99 (s, 1H),6.97 (br s, 2H), 11.25 (s, 1H).

Step 2: Preparation of5-Amino-3-(2′,3′-O-isopropylidene-5′-N-tert-butoxycarbonyl-L-valinyl)-β-D-ribofuranosyl)-thiazolo[4,5-d]pyrimidine-2,7-dione(23)

To a solution of N-butoxycarbonyl-(L)-valine (671 mg, 2.81 mmol) in THF(9 mL) at 0° C. was added EDC (588 mg, 3.07 mmol). The resultanthomogeneous mixture was stirred 45 min at 0° C., at which point it hadbecome heterogeneous, and solid acetonide 2 from Step 1 above (1.00 g,2.81 mmol) was added as one portion. Subsequently added was solid DMAP(522 mg, 4.27 mmol). The reaction mixture was permitted to reach roomtemperature, and stirred an additional 5 h, whereupon it wasconcentrated at 25° C. via rotary evaporation to a yellow syrup. Theresidue was dissolved in EtOAc (50 mL), partitioned with 1 N HCl (10 mL)followed by neutralization of acid with saturated aqueous NaHCO₃ (10mL). The acidic aqueous phase was further extracted with EtOAc (2×50mL), and then partitioned with the basic aqueous phase. The combinedorganic phases were dried over Na₂SO₄, filtered through a short pad ofSiO₂, and concentrated, affording 1.480 g (96%) of Boc-protected aminoacid ester 23 as a foam: mp 158° C. (dec); ¹H(CDCl₃) δ 0.86 (d, J=7.0,3H), 0.95 (d, J=7.0, 3H), 1.35 (s, 3H), 1.44 (s, 9H), 1.56 (s, 3H), 1.75(br s, 1H), 2.08-2.19 (m, 1H), 4.20-4.24 (m, 2H), 4.30-4.37 (m, 1H),4.56 (dd, J=11.0, 5.9, 1H), 4.96 (dd, J=6.2, 3.7, 1H), 5.11 (br d,J=8.8, 1H), 5.29 (br d, J=6.6, 1H), 5.88 (br s, 2H), 6.23 (s, 1H).

Step 3: Preparation of5-Amino-3-(5′-O-L-valinyl-β-D-ribofuranosyl)thiazolo[4,5-d]pyrimidine-2,7-dioneDihydrochloride (24)

A stream of HCl gas was passed through a bubbler of concentrated H₂SO₄,and subsequently directed (via fritted dispersion tube) into a 250 mL3-neck Morton flask containing dry isopropyl acetate (80 mL) at 0° C.until a saturated solution was obtained. To this was added a solution ofthe Boc-amino acid ester from Step 2 above (5.53 g, 9.95 mmol) inisopropyl acetate (30 mL), resulting in the formation of a white solidprecipitate within 5 min. To this was added 10% (v/v) IPA (11 mL). Thereaction mixture was warmed to room temperature, then stirred 12 h. Theheterogeneous reaction mixture was diluted with dry toluene (100 mL).Filtration using a medium pore scintered glass funnel under N₂ providedan off-white, amorphous solid. Trituration of the solid in dry THF wasfollowed by filtration and vacuum drying at 65° C., affording 3.677 g(81%) of the title compound 24 as a white solid: mp 166-68° C. (dec); ¹H(DMSO-d₆) δ 0.90 (d, J=7.0, 3H), 0.94 (d, J=7.0, 3H), 2.14-2.18 (m, 1H),3.83-3.85 (m, 1H), 3.96-4.00 (m, 1H), 4.23-4.28 (m, 2H), 4.42 (dd,J=11.7, 3.4, 1H), 4.75 (dd, J=10.3, 5.5, 1H), 5.81 (d, J=4.4, 1H), 6.46(br s, 3H), 7.23 (br s, 2H), 8.47 (s, 3H), 11.5 (br s, 1H). Elementalanalysis for C₁₅H₂₁N₅O₇S.2HCl: calc'd: C, 36.89; H, 4.75; Cl, 14.52; N,14.34; S, 6.57. Found: C, 37.03: H, 4.74; Cl, 14.26; N, 14.24; S, 6.42.

Example 285-Acetylamino-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)thiazolo[4,5-d]pyrimidine-2,7(6H)-dione(74)

Step 1: Preparation of5-Acetylamino-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)thiazolo[4,5-d]pyrimidine-2,7(6H)-dione (74)

Anhydrous 21 (8.0 g, 39.5 mmol) was dissolved in dry pyridine (65 mL).DMAP (3.1 g, 25.3 mmol) and acetic anhydride (19.1 mL 202.4 mmol) wereadded sequentially. The reaction was allowed to progress for 2 h at roomtemperature, whereupon it was quenched with saturated NaHCO₃ (100 mL)and extracted with DCM (3×200 mL). The organic phase was concentrated,and then triturated with ether. This provided 12.5 g (103%) of slightlyimpure5-acetylamino-3-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)thiazolo-[4,5-d]pyrimidin-2,7(6H)-dioneas a white solid 74: mp 246.7-248.1° C.; R_(f)=0.20 (SiO₂, 50%EtOAc—CHCl₃); ¹H NMR (400 MHz, d₆-DMSO) δ 12.23 (s, 1H), 11.85 (s, 1H),5.97 (m, 2H), 5.48 (t, J=6, 1H), 4.35-4.40 (m, 1H), 4.25-4.31 (m, 1H),4.08-4.18 (m, 1H), 2.49 (s, 3H), 2.07 (s, 3H), 2.01 (s, 3H), 2.00 (s,3H).

Example 295-Amino-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)thiazolo[4,5-d]pyrimidine-2,7(6H)-dione(75)

Step 1: Preparation of 5-Amino-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)thiazolo[4,5-d]pyrimidine-2,7(6H)-dione(75)

To a suspension of 21 (5.00 g, 15.8 mmol) in acetonitrile (160 mL) at 0°C. was added successively Et₃N (11.0 mL, 79.0 mmol), DMAP (195 mg, 1.59mmol), and Ac₂O (4.47 mL, 47.4 mmol). The reaction mixture was stirredat room temperature for 2 h, whereupon it was concentrated to a brownsyrup. The residue was purified by flash column chromatography (silica,MeOH/CHCl₃=1-10%) to afford 6.22 g (89%) of triacetate 75 as a whitesolid: mp 198-199° C.; ¹H (400 MHz, d₆-DMSO) δ 11.34 (s, 1H), 7.02 (brs, 2H), 5.90 (m, 2H), 5.51 (t, J=6.0 Hz, 1H), 4.36 (dd, J=12.4, 3.2 Hz,1H), 4.21 (m, 1H), 4.08 (q, J=6.0 Hz, 1H), 2.06 (s, 3H), 2.06 (s, 3H),2.00 (s, 3H); MS (+)-ES [M+H]⁺ m/z 443.3.

Example 305-Amino-7-ethoxy-3-β-D-ribofuranosyl-thiazolo[4,5-d]pyrimidin-2-one (77)

Step 1: Preparation of5-Acetylamino-7-ethoxy-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-thiazolo[4,5-d]pyrimidin-2-one(76)

In a manner similar to Example 2, step 1, 76 was prepared from 74 andethanol in 72% yield as a white foam: MS (+)-ES [M+H]⁺ m/z 513.R_(f)=0.45 (75% Ethyl acetate-CHCl₃).

Step 2: Preparation of5-Amino-7-ethoxy-3-β-D-ribofuranosyl-thiazolo[4,5-d]pyrimidine-2-one(77)

In a manner similar to Example 2, step 2, the title compound wasprepared from 76 in 65% yield as a white solid: ¹H NMR (400 MHz,d₆-DMSO) δ 6.87 (s, 2H), 5.85 (d, J=4.8 Hz, 1H), 5.27 (d, J=5.6 Hz, 1H),4.96 (d, J=5.2 Hz, 1H), 4.78 (m, 1H), 4.66 (m, 1H), 4.36 (m, 2H), 4.09(m, 1H), 3.74 (m, 1H), 3.58 (m, 1H), 3.40 (m, 1H), 1.29 (m, 3H); MS(+)-ES [M+H]⁺ m/z 445, [2M+H]⁺ m/z 689. R_(f)=0.2 (50% THF—CHCl₃).Elemental Analysis for C₁₂H₁₆N₄O₆S.0.25H₂O: calc'd: C, 41.31; H, 4.77;N, 16.06; S, 9.19. Found: C, 41.24; H, 4.71; N, 15.89; S, 9.06.

Example 315-Amino-7-methoxy-3-β-D-ribofuranosyl-thiazolo[4,5-d]pyrimidin-2-one(79)

Step 1: Preparation of5-Acetylamino-7-methoxy-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-thiazolo[4,5-d]pyrimidin-2-one(78)

In a manner similar to Example 2, step 1, 77 was prepared from 74 andmethanol in 65% yield as a white foam: MS (+)-ES [M+H]⁺ 499. R_(f)=0.5(75% Ethyl acetate-CHCl₃). Step 2: Preparation of5-Amino-7-methoxy-3-β-D-ribofuranosyl-thiazolo[4,5-d]pyrimidin-2-one(79)

In a manner similar to Example 2, step 2, the title compound wasprepared from 78 in 78% yield as a white solid: ¹H NMR (400 MHz,d₆-DMSO) δ 6.91 (s, 2H), 5.86 (d, J=5.2 Hz, 1H), 5.28 (d, J=5.2 Hz, 1H),4.96 (d, J=5.2 Hz, 1H), 4.77 (m, 1H), 4.66 (m, 1H), 4.09 (m, 1H), 3.90(s, 3H), 3.75 (m, 1H), 3.56 (m, 1H), 3.43 (m, 1H); MS (+)-ES [M+H]⁺ 331.R_(f)=0.2 (50% THF—CHCl₃). Elemental Analysis for C₁₁H₁₄N₄O₆S.0.25H₂O:calc'd: C, 39.46; H, 4.37; N, 16.73; S, 9.58. Found: C, 39.59; H, 4.17;N, 16.55; S, 9.52.

Example 32(5-Amino-2-oxo-3-β-D-ribofuranosyl-2,3-dihydro-thiazolo[4,5-d]pyrimidin-7-yloxymethyl)-carbamicacid ethyl ester (82)

Step 1: Preparation of 5-Amino-3-(2′,3′,5′-tris-O-triethylsilanyl-β-D-ribofuranosyl)-thiazolo[4,5-d]pyrimidin-2,7-dione(80)

To a suspension of 21 (1.00 g, 3.16 mmol) in DMF (20 mL) at roomtemperature was added successively imidazole (753 mg, 11.06 mmol), DMAP(39 mg, 0.32 mmol), and chlorotriethylsilane (1.64 mL, 9.80 mmol). Thereaction mixture was stirred at room temperature for 2 h, whereupon itwas quenched by saturated NaHCO₃ solution (20 mL). The mixture wasextracted with CHCl₃ (3×20 mL), dried over MgSO₄ and concentrated. Theresidue was purified by flash column chromatography (silica,MeOH/CHCl₃=1-5%) to afford 1.91 g (92%) of compound 80 as a white solid:¹H (400 MHz, d₆-DMSO) δ 5.99 (s, 1H), 5.62 (br s, 2H), 5.19 (dd, J=4.4,6.0 Hz, 1H), 4.35 (dd, J=2.8, 4.4 Hz, 1H), 3.99 (m, 1H), 3.77 (dd,J=7.6, 10.8 Hz, 1H), 3.68 (dd, J=4.8, 10.4 Hz, 1H), 1.10 (t, J=7.1 Hz,3H), 0.96 (t, J=7.1 Hz, 3H), 0.89 (t, J=7.1 Hz, 3H), 0.68 (q, J=7.1 Hz,2H), 0.61 (q, J=7.1 Hz, 2H), 0.54 (m, 2H); MS (+)-ES [M+H]⁺ m/z 660.0.

Step 2: Preparation of5-Amino-3-(2,3′,5′-tris-O-triethylsilanyl-β-D-ribofuranosyl)-2,3-dihydro-thiazolo[4,5-d]pyrimidin-7-yloxymethyl)-carbamicacid ethyl ester (81)

In a manner similar to Step 1 of Example 2, compound 81 was preparedfrom 80 and N-ethylurethane as a white solid in 31% yield: [M+H]⁺ 760.5;¹H NMR (400 MHz, CDCl₃) δ 6.43 (br s, 2H), 6.09 (t, J=7.6 Hz, 1H), 5.94(d, J=6.0 Hz, 1H), 5.31 (d, J=4.8 Hz, 2H), 5.19 (dd, J=6.0, 4.8 Hz, 1H),4.35 (dd, J=4.8, 2.8 Hz, 1H), 4.19 (q, J=6.4 Hz, 2H), 3.98 (m, 1H), 3.76(dd, J=10.8, 7.6 Hz, 1H), 3.68 (dd, J=10.4, 4.8 Hz, 1H), 1.29 (t, J=6.8Hz, 3H), 1.02 (t, J=8.0 Hz, 3H), 0.96 (t, J=7.6 Hz, 3H), 0.90 (t, J=8.0Hz, 3H), 0.69 (q, J=8.0 Hz, 2H), 0.61 (q, J=8.0 Hz, 2H), 0.55 (m, 2H);[M+H]⁺ 760.5.

Step 3: Preparation of(5-Amino-2-oxo-3-β-D-ribofuranosyl-2,3-dihydro-thiazolo[4,5-d]pyrimidin-7-yloxymethyl)-carbamicacid ethyl ester (82)

A solution of 81 (244 mg, 321 μmol), 5M HF in pyridine (321 μL, 1.60mmol) and THF (3.20 mL) were stirred at room temperature for 5 h.Removal of the solvents under vacuum left a residue that was purified byflash chromatography (SiO₂, 10% MeOH—CHCl₃) to afford 82 (119 mg, 90%)as a white solid: ¹H NMR (400 MHz, d₆-DMSO) δ 8.43 (br s, 1H), 7.76 (brs, 2H), 5.82 (d, J=5.2 Hz, 1H), 5.78 (s, 2H), 5.32 (d, J=5.6 Hz, 1H),5.24 (dd, J=6.0, 4.8 Hz, 1H), 5.00 (d, J=5.6 Hz, 1H), 4.82 (q, J=5.6 Hz,1H), 4.68 (t, J=6.0, 1H), 4.11 (q, J=5.2 Hz, 1H), 4.09 (q, J=7.2 Hz,2H), 3.78 (q, J=5.6 Hz, 1H), 3.60 (m, 1H), 3.46 (m, 1H), 1.21 (t, J=7.2Hz, 3H); [M+H]⁺ 418.2.

Example 33(5-Amino-2-oxo-3-β-D-ribofuranosyl-2,3-dihydro-thiazolo[4,5-d]pyrimidin-7-yloxymethyl)-methyl-carbamicacid ethyl ester (84)

Step 2: Preparation of(5-Amino-2-oxo-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-2,3-dihydro-thiazolo[4,5-d]pyrimidin-7-yloxymethyl)-methyl-carbamicacid ethyl ester (83)

In a manner similar to Example 2, step 1, compound 83 was prepared from75 and N-methyl-N-(hydroxymethyl)urethane as a white solid in 24% yield:R_(f)=0.4 (33% EtOAc—CHCl₃); ¹H NMR (400 MHz, CDCl₃) δ 11.49 (br s, 1H),6.08 (d, J=4.0 Hz, 1H), 5.75 (t, J=6.0 Hz, 1H), 5.53 (s, 2H), 4.49 (dd,J=13.5, 8.4 Hz, 1H), 4.30 (m, 5H), 3.62 (q, J=7.2 Hz, 2H), 2.30 (s, 3H),2.12 (s, 3H), 2.09 (s, 3H), 2.08 (s, 3H), 1.36 (t, J=6.8 Hz, 3H), 1.20(t, J=6.8 Hz, 3H); [M+H]⁺ 614.2.

Step 2: Preparation of(5-Amino-2-oxo-3-β-D-ribofuranosyl-2,3-dihydro-thiazolo[4,5-d]pyrimidin-7-yloxymethyl)-methyl-carbamicacid ethyl ester (84)

In a manner similar to Example 1, step 4, the title compound wasprepared from 83 as a white solid in 20% yield: ¹H NMR (400 MHz,d₆-DMSO) δ 7.86 (br s, 2H), 5.82 (d, J=4.8 Hz, 1H), 5.47 (s, 2H), 5.31(d, J=5.2 Hz, 1H), 5.00 (d, J=5.6 Hz, 1H), 4.82 (q, J=5.2 Hz, 1H), 4.67(q, J=5.6 Hz, 1H), 4.18 (q, J=6.4 Hz, 2H), 4.12 (m, 1H), 3.78 (q, J=6.0Hz, 1H), 3.60 (m, 1H), 3.47 (m, 1H), 3.30 (s, 3H), 1.27 (t, J=6.8 Hz,3H); [M+H]⁺ 432.3.

Example 345-Amino-7-(5-methyl-2-oxo-[1,3]dioxol-4-ylmethoxy)-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-thiazolo[4,5-d]pyrimidin-2-one(85)

Step 1: Preparation of5-Amino-7-(5-methyl-2-oxo-[1,3]dioxol-4-ylmethoxy)-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-thiazolo[4,5-d]pyrimidin-2-one(85)

To a solution of triacetate 75 (1.55 g, 3.50 mmol) in THF (50 mL) at 0°C. was added polymer supported-triphenylphosphine (4.95 g, 10.50 mmol,Argonaut). To this mixture was added4-hydroxymethyl-5-methyl-[1,3]dioxol-2-one (0.91 g, 7.00 mmol), preparedaccording to the procedure of Alepegiani, Syn. Comm., 22(9), 1277-82(1992) Diethyl azodicarboxylate (0.73 ml, 4.60 mmol) was then addeddropwise. The resulting mixture was stirred at room temperature for 48h, filtered and washed with MeOH and CHCl₃. The filtrate wasconcentrated and purified by flash column chromatography (silica,acetone/CHCl₃=10-20%) to afford dioxolone derivative 85 (1.38 g, 71%) aswhite solid: ¹H (400 MHz, d₆-DMSO); δ 7.06 (s, 2H), 6.00 (d, J=4.0 Hz,1H), 5.92 (dd, J=6.6, 4.4 Hz, 1H), 5.56 (t, J=6.4 Hz, 1H), 5.30 (s, 2H),4.38 (dd, J=11.6, 3.6 Hz, 1H), 4.25 (t, J=3.6 Hz, 1H), 4.10 (q, J=6.0Hz, 1H), 2.23 (s, 3H), 2.08 (s, 3H), 2.07 (s, 3H), 2.00 (s, 3H); MS(+)-ES [M+H]⁺ m/z 555.3. Elemental Analysis calc'd forC₂₁H₂₂N₄O₁₂S.Me₂CO: C, 47.06; H, 4.61; N, 9.15; S, 5.23. Found: C,47.25; H, 4.37; N, 9.53; S, 5.52.

Example 355-Amino-7-(5-methyl-2-oxo-[1,3]dioxol-4-ylmethoxy)-3-β-D-ribofuranosyl-thiazolo[4,5-d]pyrimidin-2-one(87)

Step 1: Preparation of5-Amino-7-(5-methyl-2-oxo-[1,3]dioxol-4-ylmethoxy)-3-(2′,3′,5′-tris-O-triethylsilanyl-β-D-ribofuranosyl)-thiazolo[4,5-d]pyrimidin-2-one(86)

In a manner similar to Example 34, compound 86 was prepared from 80 and4-hydroxymethyl-5-methyl-[1,3]dioxol-2-one as a white solid in 45%yield: ¹H NMR (400 MHz, CDCl₃) δ 6.06 (d, J=6.0 Hz, 1H), 5.21 (dd,J=6.0, 4.8 Hz, 1H), 5.18 (d, J=3.2 Hz, 2H), 4.94 (br s, 2H), 4.38 (dd,J=4.8, 2.8 Hz, 4H), 400 (m, 3H), 379 (dd, J=11.2, 8.0 Hz, 1H), 3.69 (dd,J=10.8, 5.2 Hz, 1H), 2.23 (s, 3H), 1.02 (t, J=8.0 Hz, 3H), 0.96 (t,J=7.6 Hz, 3H), 0.89 (t, J=8.4 Hz, 3H), 0.70 (q, J=7.6 Hz, 2H), 0.61 (q,J=8.0 Hz, 2H), 0.53 (m, 2H); [M+H]⁺ 771.5.

Step 2: Preparation of5-Amino-7-(5-methyl-2-oxo-[1,3]dioxol-4-ylmethoxy)-3-β-D-ribofuranosyl-thiazolo[4,5-d]pyrimidin-2-one(87)

In a manner similar to Steps 3 of Example 32, the title compound wasprepared from 86 as a white solid in 89% yield: ¹H NMR (400 MHz,d₆-DMSO) δ 7.03 (br s, 2H), 5.90 (d, J=5.2 Hz, 1H), 5.33 (s, 2H), 5.02(d, J=4.8 Hz, 1H), 4.83 (q, J=5.6 Hz, 1H), 4.71 (t, J=6.0 Hz, 1H), 4.14(q, J=5.2 Hz, 1H), 3.80 (q, J=4.8 Hz, 1H), 3.62 (m, 1H), 3.47 (m, 1H),2.27 (s, 3H); [M+H]⁺ 429.2.

Example 365-Amino-3-β-D-ribofuranosyl-3H-thiazolo-[4,5-d]pyrimidin-2-one (90)

Step 1: Preparation of5-Amino-7-thioxo-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-thiazolo[4,5-d]pyrimidin-2-one(88)

To a solution of 75 (1 g, 2.26 mmol) in pyridine (50 mL) was added atroom temperature P₂S₅ (2.13 g, 4.79 mmol). The solution was refluxedgently (bath temperature 130-140° C.) for 29 h. The reaction mixture wasevaporated to dryness in vacuo. The excess P₂S₅ was decomposed by theaddition of H₂O (40 mL) at 60° C. The mixture was stirred for 1 h at 60°C. and then cooled to room temperature. The mixture was extracted withCHCl₃ (3×40 mL). The dried (MgSO₄) organic layer was evaporated to yielda syrup, which was purified by flash column chromatography (silica,acetone/CHCl₃=15%) to afford 0.93 g (90%) of 88 as a yellow solid: ¹H(400 MHz, d₆-DMSO) δ 12.50 (s, 1H), 7.35 (br s, 2H), 5.89 (m, 2H), 5.51(t, J=6.4 Hz, 1H), 4.36 (dd, J=12.0, 4.0 Hz, 1H), 4.24 (m, 1H), 4.10 (q,J=6.0 Hz, 1H), 2.07 (s, 3H), 2.06 (s, 3H), 2.01 (s, 3H); MS (+)-ES[M+H]⁺ m/z 459.3.

Step 2: Preparation of5-Amino-3-(2′,3′,5′-tri-O-acetyl-β-D-ribofuranosyl)-3H-thiazolo[4,5-d]pyrimidin-2-one(89)

A suspension of Raney® 2800 nickel (3 big spatula, pre-washed with H₂O,MeOH and acetone) in acetone (50 mL) was stirred at refluxing for 1 h.Triacetate 88 (0.93 g, 2.03 mmol) was subsequently added into the abovesuspension at reflux. The mixture was stirred for 5 min, cooled to roomtemperature over 30 min. The reaction was quenched by bubbling H₂S (g)into the mixture for 2 h. The resulting mixture was filtered through ashort pad of Celite® and washed with EtOH. The filtrate was concentratedand purified by flash column chromatography (silica, MeOH/CHCl₃=1-2%) toafford 0.52 g (60%) of 89 as a white solid: mp 121-123° C.; ¹H (400 MHz,d₆-DMSO) δ 8.38 (s, 1H), 6.93 (s, 2H), 6.03 (d, J=3.6 Hz, 1H), 5.93 (dd,J=6.4, 3.6 Hz, 1H), 5.58 (t, J=6.0 Hz, 1H), 4.38 (dd, J=11.6, 3.6 Hz,1H), 4.26 (m, 1H), 4.11 (q, J=6.0 Hz, 1H), 2.08 (s, 3H), 2.07 (s, 3H),2.00 (s, 3H); MS (+)-ES [M+H]⁺ m/z 427.2. Elemental Analysis calc'd forC₁₆H₁₈N₄O₈S.0.5 CH₃OH.0.25H₂O: C, 44.34; H, 4.62; N, 12.54; S 7.17.Found: C, 44.54; H, 4.88; N, 12.16; S, 7.17.

Step 3: Preparation of5-Amino-3-β-D-ribofuranosyl-3H-thiazolo[4,5-d]pyrimidin-2-one (90)

To a solution of 89 (0.52 g, 1.22 mmol) in MeOH (20 mL) was added K₂CO₃(25 mg, 0.18 mmol). The reaction was stirred at room temperatureovernight, then neutralized with AcOH (21 μL, 0.36 mmol). The resultingmixture was stirred at room temperature for additional 30 min,concentrated, and triturated with H₂O (2 ml) to afford 0.33 g ofcompound 90 (89%) as a white solid: mp 220° C. (Dec); ¹H (400 MHz,d₆-DMSO) δ 8.34 (s, 1H), 6.85 (s, 2H), 5.90 (d, J=4.8 Hz, 1H), 5.31 (d,J=5.6 Hz, 1H), 4.98 (d, J=5.6 Hz, 1H), 4.81 (q, J=5.2 Hz, 1H), 4.67 (t,J=6.0 Hz, 1H), 4.11 (q, J=5.2 Hz, 1H), 3.77 (dd, J=10.8, 4.8 Hz, 1H),3.58 (m, 1H), 3.44 (m, 1H); MS (+)-ES [M+H]⁺ m/z 301.1. ElementalAnalysis calc'd for C₁₀H₁₂N₄O₅S.0.3H₂O: C, 39.29; H, 4.15; N, 18.33; S10.49. Found: C, 39.51; H, 4.18; N, 17.95; S, 10.27.

Example 375-Amino-3-(2′,3′-di-O-acetyl-β-D-ribofuranosyl)-3H-thiazolo[4,5-d]pyrimidin-2-one(93)

Step 1: Preparation of5-Amino-3-(5′-O-tert-butyl-dimethylsilanyl-β-D-ribofuranosyl)-3H-thiazolo[4,5-d]pyrimidin-2-one(91)

To a solution of 90 (0.68 g, 2.28 mmol) in DMF (10 mL) was addedimidazole (0.54 g, 7.93 mmol) and tert-butyldimethylsilyl chloride (0.68g, 4.56 mmol) sequentially. The reaction mixture was stirred at roomtemperature for 2 h, at which point it was concentrated and purified byflash column chromatography (silica, MeOH/CHCl₃; gradient=5-20%) toafford 0.49 g (52%) 91 as a white solid: ¹H (400 MHz, d₆-DMSO) δ 8.33(s, 1H), 6.87 (s, 2H), 5.90 (d, J=4.0 Hz, 1H), 5.33 (d, J=5.6 Hz, 1H),5.00 (d, J=5.2 Hz, 1H), 4.79 (q, J=5.2 Hz, 1H), 4.16 (q, J=5.2 Hz, 1H),3.77 (m, 2H), 3.64 (dd, J=12.0, 7.2 Hz, 1H), 0.84 (s, 9H), 0.00 (s, 6H);MS (+)-ES [M+H]⁺ m/z 415.4.

Step 2: Preparation of 5-Amino-3-(2′,3′-di-O-acetyl,5′-O-tert-butyl-dimethylsilanyl-β-D-ribofuranosyl)-3H-thiazolo[4,5-d]pyrimidin-2-one(92)

To a solution of 91 (0.20 g, 0.48 mmol) in acetonitrile (5 mL) at 0° C.was added successively Et₃N (0.26 mL, 1.86 mmol) and Ac₂O (91 μL, 0.96mmol). The reaction mixture was stirred at room temperature for 24 h,whereupon it was concentrated and purified by flash columnchromatography (silica, acetone/CHCl₃: gradient=5-10%) to afford 0.22 g(92%) of 92 as a white solid: ¹H (400 MHz, d₆-DMSO) δ 8.36 (s, 1H), 6.90(s, 2H), 6.00 (m, 2H), 5.57 (t, J=6.0 Hz, 1H), 4.07 (q, J=5.2 Hz, 1H),3.77 (m, 2H), 2.07 (s, 3H), 2.06 (s, 3H), 0.83 (s, 9H), 0.00 (d, J=2.4Hz, 6H); MS (+)-ES [M+H]⁺ m/z 499.5.

Step 3: Preparation of5-Amino-3-(2′,3′-di-O-acetyl-β-D-ribofuranosyl)-3H-thiazolo[4,5-d]pyrimidin-2-one(93)

To a solution of 92 (0.22 g, 0.44 mmol) in THF (5 mL) in a plastic vialwas added HF/pyridine (0.70 mL). The reaction was stirred for 2 h,concentrated and purified by flash column chromatography (silica,MeOH/CHCl₃: gradient=5-10%) to afford 0.17 g (100%) of the titlecompound as a white solid: mp 109-111° C.; ¹H (400 MHz, d₆-DMSO) δ 8.37(s, 1H), 6.91 (s, 2H), 6.00 (m, 2H), 5.48 (t, J=6.0 Hz, 1H), 4.91 (t,J=6.0 Hz, 1H), 4.04 (dd, J=10.4, 6.0 Hz, 1H), 3.64 (m, 1H), 3.52 (m,1H), 2.08 (s, 3H), 2.05 (s, 3H); MS (+)-ES [M+H]⁺ m/z 385.3. ElementalAnalysis calc'd for C₁₄H₁₆N₄O₇S.0.5 CH₃OH.0.2 CHCl₃: C, 41.61; H, 4.32;N, 13.21; S 7.56. Found: C, 41.73; H, 4.29; N, 12.86; S, 7.33.

Example 38[2-Ethoxymethyl-1-(2-hydroxy-2-methyl-propyl)-1H-imidazo[4,5-c]quinolin-4-yl]-carbamicacid ethyl ester (39)

Step 1: Preparation of[2-Ethoxymethyl-1-(2-hydroxy-2-methyl-propyl)-1H-imidazo[4,5-

In a manner similar to step 1 of Example 8 except, substituting MeOH asthe solvent, was prepared the title compound from1-(4-amino-2-ethoxymethyl-imidazo[4,5-c]quinolin-1-yl)-2-methyl-propan-2-ol(38) (prepared according to the procedure given in InternationalPublication No. WO 94/17043) and diethyl pyrocarbonate as an oil in 39%yield: ¹H NMR (400 MHz, CDCl₃) δ 8.36 (d, J=8.0 Hz, 1H), 8.05 (d, J=8.0Hz, 1H), 7.70 (t, J=7.2 Hz, 1H), 7.61 (t, J=8.0 Hz, 1H), 4.96 (br s,2H), 4.80 (s, 2H), 4.39 (q, J=7.2 Hz, 2H), 3.62 (q, J=7.2 Hz, 2H), 1.40(t, J=7.2 Hz, 3H), 1.36 (br s, 6H), 1.24 (t, J=6.8 Hz, 3H); MS (+)-ES[M+H]⁺ 387.4 m/z.

6.4 Masking Effect of TLR7 Ligand Prodrugs

A typical experiment would use human peripheral blood mononuclear cells(PBMC) isolated from a healthy donor and placed in replicate cellculture wells; typically, 2×10⁶ to 5×10⁶ cells are placed in each well.The PBMC are incubated in the absence of test compounds at 37° C. in ahumidified atmosphere containing 5% CO₂ for 24 hours to allowstabilization to the culture conditions, and then 100 micromolarisatoribine, the TLR7 ligand and a corresponding TLR7 ligand prodrug areadded to separate wells containing PBMC from the same donor; untreatedcontrols are included. The concentrations of TLR7 ligand and TLR7 ligandprodrug may be varied to suit the particular experiment, and the PBMCcultures are then incubated at 37° C. in a humidified atmospherecontaining 5% CO₂ for a period of time ranging from two hours to 48hours. Samples of cell culture supernate media are taken during theincubation. These are assayed for cytokine production by ELISA.Additionally the amount of TLR7 ligand and TLR7 ligand prodrug remainingat the end of the incubation may be assayed by LC-MS. Cytokineproduction is calculated relative to production in the isatoribinecontrol, following subtraction of the cytokine production in untreatedcontrols. The cytokine results are compared to determine the extent thatthe TLR7 ligand is more active than the corresponding TLR7 ligandprodrug.

Thus, if the TLR7 ligand generates more interferon alpha (a convenientlymeasured cytokine) than does the corresponding TLR7 ligand prodrug aftera similar duration of exposure and concentration, the TLR7 ligandprodrug may be deemed a “masked” TLR7 ligand prodrug. The magnitude ofreduction in cytokine production that constitutes “masking” may be aslittle as a 25% reduction relative to the parent TLR, since this wouldafford a corresponding increase in administered dose for a given levelof tolerability.

Tables 9 through 14 provide data illustrating that TLR7 ligands ofmultiple chemical classes can be masked. The examples shown demonstratesubstantial masking relative to the parent TLR7 ligand. The chemicalsubstitutions shown are exemplary, and in no way restrictive of theinvention, since additional chemical substitutions may also exhibitmasking and are contemplated in the invention. Masking can be achievedby introduction of substitutions at a range of locations on any TLR7ligand, and as shown can incorporate a variety of chemical linkages. Itwill be appreciated that the preferred substitution and linkage may varyfor different parent TLR7 ligands.

TABLE 9 Masking of Isatoribine Prodrugs Parent molecule Amount of INFarelative to that and its prodrugs Compound No. induced by isatoribine at100 μM, % Parent molecule: 21 100 Isatoribine Prodrug: 24 1 Amino acidester Prodrug: 93 0 Deoxy Prodrug: 77 0 6-Ethoxy Prodrug: 79 0 6-MethoxyProdrug: 84 0 Aminal Prodrug: 82 0 Aminal Prodrug: 85 0 Dioxolenone

The masked property of isatoribine prodrugs can be demonstrated in aPBMC assay. The results of the PBMC assay (Table 9) show the amount ofINFa released after exposure of the parent compound and its prodrugs foreither 8 hours (val-isatoribine, 24) or 24 hours (other prodrugs) at theinitial concentration of 100 μM. The amount of the released INFa wasnormalized to that induced by 100 μM of isotoribine at 100 μM in thesame blood donor with the same exposure time.

TABLE 10 Masking of Loxoribine Prodrugs Parent molecule Amount of INFarelative to that and its prodrugs Compound No. induced by isatoribine at100 μM, % Parent molecule: 17 50 Loxoribine Prodrug: 45 0 6-EthoxyProdrug: 43 0 Deoxy Prodrug: 68 0 Valyl ester

The masked property of loxoribine prodrugs can be demonstrated in a PBMCassay. The results of the PBMC assay (Table 10) show the amount of INFareleased after exposure of the parent compound and its prodrugs for 24hours at the initial concentration 100 μM. The amount of the releasedINFa was normalized to that induced by 100 μM of isotoribine at 100 μMin the same blood donor with the same exposure time.

TABLE 11 Masking of Imiquimod Prodrugs Parent molecule Amount of INFarelative to that and its prodrugs Compound No. induced by isatoribine at100 μM, % Parent molecule: 31 60-76* Imiquimod Prodrug: 34 0 Pentylcarbamate Prodrug: 50 0 Ethyl carbamate *Results of two experiments withthree different donors

The masked property of imiquimod prodrugs can be demonstrated in a PBMCassay. The results of the PBMC assay (Table 11) show the amount of INFareleased after exposure of the parent compound and its prodrugs for 24hours at the initial concentration 100 μM. The amount of the releasedINFa was normalized to that induced by 100 μM of isatoribine at 100 μMin the same blood donor with the same exposure time.

TABLE 12 Masking of Resiquimod Prodrugs Parent molecule and Amount ofINFa relative to that its prodrugs Compound No. induced by isatoribineat 100 μM, % Parent 39  95 @ 1 μM molecule: Resiquimod Prodrug: 38 9 @100 μM Ethyl Carbamate

The masked property of resiquimod prodrugs can be demonstrated in a PBMCassay. The results of the PBMC assay (Table 12) show the amount of INFareleased after exposure of the parent compound and its prodrugs for 24hours at the initial concentrations of either 1 or 100 μM. The amount ofthe released INFa was normalized to that induced by 100 μM ofisatoribine at 100 μM in the same blood donor with the same exposuretime.

TABLE 13 Masking of Bropirimine Prodrugs Parent molecule Amount of INFarelative to that and its prodrugs Compound No. induced by isatoribine at100 μM, % Parent molecule: 35 22 Bropirimine Prodrug: 48 0 DeoxyProdrug: 37 0 Ethoxy Prodrug: 36 0 Ethyl carbamate Prodrug: 49 0 Pentylcarbamate

The masked property of bropirimine prodrugs can be demonstrated in aPBMC assay. The results of the PBMC assay (Table 13) show the amount ofINFa released after exposure of the parent compound and its prodrugs for24 hours at the initial concentration of 100 μM. The amount of thereleased INFa was normalized to that induced by 100 μM of Isatoribine at100 μM in the same blood donor with the same exposure time.

TABLE 14 Masking of Adenine Prodrugs Parent molecule Amount of INFarelative to that and its prodrugs Compound No. induced by isatoribine at100 μM, % Parent molecule 29 128 @ 0.1 μM   Prodrug: 65 0 @ 100 μMMethoxy Prodrug: 64  0 @ 10 μM Ethoxy Prodrug: 62  0 @ 0.1 μM DeoxyProdrug: 51 18 @ 32 μM Ethyl carbonate Prodrug: 54 15 @ 10 μM Pentylcarbonate

The masked property of adenine prodrugs can be demonstrated in a PBMCassay. The results of the PBMC assay (Table 14) show the amount of INFareleased after exposure of the parent compound and its prodrugs for 24hours at different initial concentrations specified in the table. Theamount of the released INFa was normalized to that induced by 100 μM ofisatoribine at 100 μM in the same blood donor with the same exposuretime.

TLR7 ligand prodrugs can also be assessed in vitro for their conversionto the active parent TLR7 ligand. This can be measured by incubation ofthe prodrug in blood, plasma, or in a cell culture of hepatocytes. Atselected time intervals, samples are taken to determine the amount ofprodrug remaining and the amount of TLR7 ligand produced. Suchdeterminations are readily made by use of analytical tools known in theart such as LC-MS. The determination of the extent of conversion of amasked TLR7 ligand prodrug to the parent TLR7 ligand is useful ininterpreting data wherein masking is apparent at shorter times butdiminishes upon long incubations in the PBMC assay described herein. Therate of conversion of the prodrug to the TLR7 ligand may be determinedto ensure that the cytokine results arise predominately from exposure toprodrug rather than from exposure to TLR7 ligand generated by rapidconversion of the prodrug under the conditions of the experiment.

6.5 Biological Testing of TLR7 Ligand Prodrugs Demonstrating

Increased Oral Availability and Decreased Side-Effects

Oral Availability

The improved bioavailability of TLR7 ligand prodrugs can be assessed byperforming studies in vivo. In such experiments, the candidate prodrugsare administered by oral administration to mice, rats, monkeys, and/ordogs, and blood samples are taken at selected intervals. The bloodsamples are analysed for both the prodrug and the desired TLR7 ligand.Additional blood or liver samples may be analyzed for the presence ofinterferons and other cytokines that indicate functional activation ofthe TLR7 pathway in vivo. Desired candidates will demonstrate a bloodexposure to the prodrug and also demonstrate a blood exposure to thedesired TLR7 ligand of about 10% to 99% of the applied dose, as measuredon a molar basis.

A representative example is the result obtained with the TLR7 ligandprodrug val-isatoribine (24), which as described below in the mouse anddog generated significant amounts of the parent TLR7 ligand isatoribine(21) in the blood. See U.S. patent application Ser. No. 10/305,061(incorporated herein by reference in its entirety).

Interferon Alpha (Mu-IFN-α) Concentrations in Mice

The normal mouse provides a useful system for the assessment of thedegree to which the inventions described herein provide materialimprovement in the oral delivery of 21 (isatoribine). Not only can onemeasure the plasma concentrations of isatoribine arising from oraladministration of the said prodrug(s) but also the extensiveimmunological research conducted in the mouse has provided reagentssuitable for measuring the levels of interferon alpha, a cytokine ofinterest reflecting one of the desired biologic activities ofisatoribine.

We have used the murine system in a series of experiments thatdemonstrate that 24, the 5′-valine ester of 21 (val-isatoribine) elicitsan interferon response substantially improved over that resulting fromadministration of isatoribine itself.

Table 15 records the results of an assay for murine interferon alpha inthe plasma of mice that were dosed two times with isatoribine,formulated in bicarbonate, at a level of 50 mg/kg by the oral route. Itis evident that no interferon was measurable even when the dose wasrepeated after an interval of four hours.

TABLE 15 Interferon Alpha (Mu-IFN-α) Plasma Concentration (pg/mL) inMice Following Two Oral 50 mg/kg Doses of Isatoribine 4 Hours ApartTime, h Individual Value Mean SD First Dose 0.00 BQL⁵⁰ BQL¹²⁵ BQL⁵⁰ 0.000.00 0.03 BQL²⁵ BQL²⁵⁰ BQL²⁵ 0.00 0.00 0.08 BQL²⁵ BQL²⁵ BQL²⁵ 0.00 0.000.25 BQL⁵⁰ BQL²⁵ BQL²⁵ 0.00 0.00 0.50 BQL²⁵ BQL²⁵ BQL²⁵ 0.00 0.00 1.00BQL²⁵ BQL²⁵ BQL²⁵ 0.00 0.00 1.50 BQL¹⁰⁰ BQL²⁵ BQL²⁵ 0.00 0.00 2.00 BQL²⁵BQL⁷⁵ BQL²⁵ 0.00 0.00 3.00 BQL²⁵ BQL²⁵ BQL²⁵ 0.00 0.00 4.00 BQL²⁵ BQL²⁵BQL²⁵ 0.00 0.00 Second Dose 4.03 BQL²⁵ BQL²⁵ BQL²⁵ 0.00 0.00 4.08 BQL²⁵BQL²⁵ BQL²⁵ 0.00 0.00 4.25 BQL²⁵ BQL²⁵ BQL²⁵ 0.00 0.00 4.50 BQL⁵⁰BQL^(37.5) BQL⁵⁰ 0.00 0.00 5.00 BQL⁵⁰ BQL⁵⁰ BQL⁵⁰ 0.00 0.00 5.50BQL^(37.5) BQL^(37.5) BQL^(37.5) 0.00 0.00 6.00 BQL⁵⁰ BQL^(41.3)BQL^(37.5) 0.00 0.00 7.00 BQL⁵⁰ BQL⁵⁰ BQL⁵⁰ 0.00 0.00 8.00 BQL⁵⁰ BQL²⁵BQL⁵⁰ 0.00 0.00 BQL^(n)—Below Elevated Quantifiable Limit <n pg/mL.

Table 16 records the results of assays for murine interferon alpha inthe plasma of mice that first were dosed with bicarbonate and then fourhours later were dosed orally with isatoribine, formulated inbicarbonate, at a level of 50 mg/kg. Interferon was reported in theplasma from four mice, including two that had received the bicarbonatevehicle dose. All the values reported in this experiment were low, andthe reported interferon levels were not consistently reported for allthree mice assessed at each time point, suggesting that these signalsmay be artifacts arising from measurement near the lower limits of theassay.

TABLE 16 Interferon Alpha (Mu-IFN-α) Plasma Concentration (pg/mL) inMice Following One Vehicle Dose and One 50 mg/kg Doses of Isatoribine 4Hours Later Time, h Individual Value Mean SD First Dose 0.00 BQL⁵⁰BQL¹⁰⁰ BQL^(62.5) 0.00 0.00 0.03 BQL⁵⁰ BQL⁵⁰ BQL^(37.5) 0.00 0.00 0.08BQL⁵⁰ BQL⁵⁰ BQL⁵⁰ 0.00 0.00 0.25 BQL⁵⁰ BQL^(62.5) BQL⁵⁰ 0.00 0.00 0.50BQL⁵⁰ BQL⁵⁰ BQL⁵⁰ 0.00 0.00 1.00 BQL⁵⁰ BQL⁵⁰ BQL¹⁰⁰ 0.00 0.00 1.50 BQL⁵⁰BQL¹⁰⁰ BQL⁵⁰ 0.00 0.00 2.00 34.9 BQL²⁵ BQL²⁵ 11.6 20.15 3.00 BQL²⁵ BQL²⁵BQL²⁵ 0.00 0.00 4.00 BQL²⁵ 35.4 BQL¹⁰⁰ 11.8 20.44 Second Dose 4.03 BQL²⁵BQL²⁵ BQL²⁵ 0.00 0.00 4.08 BQL²⁵ BQL²⁵ BQL²⁵ 0.00 0.00 4.25 BQL²⁵ BQL²⁵BQL²⁵ 0.00 0.00 4.50 BQL¹⁰⁰ BQL²⁵ 133.2 44.4 76.90 5.00 74.9 BQL⁵⁰ NR37.5 52.96 5.50 BQL²⁵⁰ BQL⁷⁵ BQL²⁵ 0.00 0.00 6.00 BQL²⁵ BQL⁷⁵ BQL⁷⁵ 0.000.00 7.00 BQL⁵⁰ BQL⁵⁰ BQL²⁵ 0.00 0.00 8.00 BQL²⁵ BQL²⁵ BQL²⁵ 0.00 0.00BQL^(n)—Below Elevated Quantifiable Limit <n pg/mL. NR—Not reportable.

Table 17 records the results of assays for murine interferon alpha inthe plasma of mice that were dosed orally with val-isatoribine,dissolved in bicarbonate, at a dose that is equivalent to 50 mg/kg ofisatoribine on a molar basis. It is evident that interferon was readilymeasurable at 1.0 hour, 1.5 hours, and 2.0 hours after dosing.Interferon was detected in all mice assayed at a given time point,indicating the reliability of the effect following val-isatoribineadministration. Thus a single administration of val-isatoribine wassuperior to either a single dose or a repeated dose of isatoribine.

TABLE 17 Plasma Concentration (pg/mL) of Interferon Alpha (Mu-IFN-α) inMice Following a Single 73.0 mg/kg Dose of Val-Isatoribine Time, hIndividual Value Mean SD 0.00 BQL BQL¹²⁵ BQL²⁵ 0.00 0.00 0.25 BQL BQLBQL 0.00 0.00 0.50 BQL²⁵ BQL²⁵ BQL 0.00 0.00 0.75 BQL BQL BQL²⁵ 0.000.00 1.00 173.2 125.1  89.0 129.1 42.24 1.50 202.9 145.9 294.8 214.575.13 2.00  49.2 137.9 138.3 108.5 51.33 3.00 BQL²⁵ NR NR 0.00 0.00 4.00BQL²⁵  27.6 BQL 9.20 15.90 5.00 BQL BQL²⁵ BQL²⁵ 0.00 0.00 BQL—Below theQuantifiable Limit <12.5 pg/mL BQL^(n)—Below the Elevated QuantifiableLimit <n pg/mL NR—Not Reportable

The data tabulated in Tables 15, 16, and 17 may be also considered fromthe point of view of the incidence of measurable interferon levels.Interferon was detected in the plasma of only 4 of the 114 mice used inthe studies of isatoribine, whereas 10 of the 30 mice dosed withval-isatoribine had detectable interferon in their plasma. Thus, theprodrug increased the proportion of mice exhibiting an interferonresponse from 4% to 30% and the magnitude of both the average and peakresponse was increased twofold (100%).

In other experiments, plasma levels of isatoribine and interferon alphawere measured in mice that were dosed with isatoribine by theintravenous route, and these levels were compared to the levels ofisatoribine and interferon alpha arising after oral administration ofval-isatoribine. These data are summarized in FIG. 1. In this figure itis evident that the levels of interferon alpha induced by oralval-isatoribine (“val-isator”) (at 50 mg/kg isatoribine molarequivalent) was similar to that from intravenous isatoribine (“isator”)at 25 mg/kg. Thus, oral val-isatoribine provides levels of isatoribineand interferon that are approximately 50% of those observed afterintravenous administration of isatoribine itself.

Beagle Dog

The effect of a prodrug (val-isatoribine, 24) on the systemic exposureto isatoribine (21) after oral administration to beagle dogs wasinvestigated. Isatoribine was prepared in sodium bicarbonate solution.Val-isatoribine and isatoribine were prepared as the followingformulations, which were chosen to ensure solubility:

Formulation 1: Isatoribine in sodium bicarbonate solution, 1 and 4mg/mL.

Formulation 2: Val-isatoribine in phosphate buffered saline, 1.62 and6.48 mg/mL, equivalent to 1 and 4 mg/mL of isatoribine on a molar basis.

Four male and four female adult beagle dogs weighing between 15 to 27 kgand approximately 1-2 years old were used at the beginning of the study.The animals were divided into 2 groups of 2 males and 2 females each.The test material was administered by gavage on Days 1 and 8, allowing a7 day washout period between administrations. Blood samples (2 mL) werecollected from each animal at predose, 15, 30 minutes, 1, 2, 3, 4, 6, 8and 10 hours into lithium heparin tubes after each dosing. The plasmawas frozen at −70° C. until analysis. The plasma was analyzed forisatoribine by an HPLC-MS/MS assay.

The pharmacokinetic parameters for isatoribine arising from isatoribineor val-isatoribine in each dog are summarized in Tables 18 and 19. Theratios for the key pharmacokinetic parameters defining the maximumconcentration (Cmax ) and total exposure as measured by the area underthe time-concentration curve (AUC) for the prodrug and the bicarbonatesolution at the 50 mg/kg dose are summarized in Table 20. For theprodrug 24, the Cmax ratio was 2.98±0.695 and the AUC ratio was2.38±0.485. These results indicate that at 50 mg/kg dose, the prodrugval-isatoribine provided substantially higher Cmax and greaterbioavailability than isatoribine in bicarbonate solution.

The ratios for the Cmax and AUC for the prodrug to the bicarbonatesolution for the 10 mg/kg dose are summarized in Table 21. For theprodrug, the Cmax ratio was 2.24±0.249 and the AUC ratio was 1.82±0.529.These results indicate that at 10 mg/kg dose, the prodrugval-isatoribine provided higher Cmax and greater bioavailability thanisatoribine in bicarbonate solution.

Thus, the maximum concentrations of isatoribine achieved after oraldosing are at least doubled, and the systemic exposure to isatoribine isenhanced by approximately 2-fold following oral administration of theprodrug val-isatoribine, compared to isatoribine itself, at both 10 and50 mg/kg dose.

TABLE 18 Pharmacokinetic Parameters of Isatoribine in Dogs dosed at 50mg/kg Dosing Period 1 2 Formulation Val- Isatoribine isatoribine Dose,mg/kg molar equivalent isatoribine Animal Number 50 50 Dog 3517322 Cmax,ng/mL 3038.7 11741.5 Tmax, h 0.50 0.50 AUC (0-inf), 15227.0 33038.1 ng ·h/mL T½, h 6.4 2.4 Dog 3521451 Cmax, ng/mL 3354.0 10652.1 Tmax, h 1.001.00 AUC (0-inf), ng · h/mL 9422.2 26552.7 T_(1/2), h 1.9 1.6 Dog3528707 Cmax, ng/mL 8915.3 20340.6 Tmax, h 0.50 0.50 AUC (0-inf), ng ·h/mL 29701.7 53273.0 T_(1/2), h 2.2 2.3 Dog 3532828 Cmax, ng/mL 6134.715987.9 Tmax, h 0.50 0.50 AUC (0-inf), ng · h/mL 12069.7 32987.0T_(1/2), h 1.4 1.6

TABLE 19 Pharmacokinetic Parameters of Isatoribine in Dogs Dosed at 10mg/kg Dosing Period 1 2 Formulation Val- Isatoribine isatoribine Dose,mg/kg molar equivalent isatoribine Animal Number 10 10 Dog 3524523 Cmax,ng/mL 4091.5 8594.6 Tmax, h 1.00 0.50 AUC (0-inf), ng · h/mL 13305.817166.2 T_(1/2), h 2.1 1.7 Dog 3526402 Cmax, ng/mL 1859.5 4047.0 Tmax, h1.00 1.00 AUC (0-inf), ng · h/mL 5774.4 10548.9 T_(1/2), h 1.6 2.2 Dog357450 Cmax, ng/mL 1620.3 4228.7 Tmax, h 0.50 1.00 AUC (0-inf), ng ·h/mL 4387.3 11158.0 T_(1/2), h 1.5 2.3 Dog 354708 Cmax, ng/mL 2781.25784.8 Tmax, h 0.50 0.50 AUC (0-inf), ng · h/mL 7522.1 12259.1 T_(1/2),h 1.6 2.0

TABLE 20 Ratio of Pharmacokinetic Parameters of Isatoribine in DogsDosed at 50 mg/kg Formulation Val- Animal Number Isatoribine isatoribineDog 3517322 Cmax Ratio 1.00 3.86 AUC Ratio 1.00 2.17 Dog 3521451 CmaxRatio 1.00 3.18 AUC Ratio 1.00 2.82 Dog 3528707 Cmax Ratio 1.00 2.28 AUCRatio 1.00 1.79 Dog 3532828 Cmax Ratio 1.00 2.61 AUC Ratio 1.00 2.73Mean Cmax Ratio N/A 2.98 SD Cmax Ratio N/A 0.695 Mean AUC Ratio N/A 2.38SD AUC Ratio N/A 0.485

TABLE 21 Ratio of Pharmacokinetic Parameters of Isatoribine in DogsDosed at 10 mg/kg Formulation Val- Animal Number Isatoribine isatoribineDog 3524523 Cmax Ratio 1.00 2.10 AUC Ratio 1.00 1.29 Dog 3526402 CmaxRatio 1.00 2.18 AUC Ratio 1.00 2.20 Dog 3527450 Cmax Ratio 1.00 2.61 AUCRatio 1.00 2.54 Dog 355708 Cmax Ratio 1.00 2.08 AUC Ratio 1.00 1.63 MeanCmax Ratio N/A 2.24 SD Cmax Ratio N/A 0.249 Mean AUC Ratio N/A 1.82 SDAUC Ratio N/A 0.529

The prodrug val-isatoribine is preferred for several reasons. First, theprodrug is easily formulated to provide a high proportion of activeagent. This results in small capsule sizes for a given dose, which is anadvantage for an oral product. Second, at the doses tested,val-isatoribine provides plasma levels of isatoribine that are wellwithin the range desirable for biologic effect after oraladministration, which is not the case for isatoribine itself.

Cynomolgus Monkey

From two to four male or female cynomolgus monkeys were used on theanimal testing study. The study compound was formulated in a vehicleappropriate for animal oral or intravenous administration. The vehiclesused were either as aqueous buffers or a solutions containing Cremophor.Animals were dosed via oral gavage or intravenous bolus injection foreach test article. Blood samples (approximately 0.5 mL) were collectedat predetermined time points (usually, pre-dose, 15, 30, and 45 minutesand at 1, 1.5, 2, 2.5, 3, 4, 8 and 24 hours post-dose), placed intotubes containing disodium EDTA. The samples were placed on wet icefollowing collection, and plasma separated as rapidly as possible. Theplasma samples were aliquoted into a single vial, and stored frozen atapproximately −20° C. until shipped on dry ice to the Sponsor. Animalswere given food and water approximately 4 hours after the dose.

The plasma samples were analyzed for a prodrug and a parent compoundusing well-known LCMS/MS quantitation techniques by triple quadrupoleinstruments, i.e Sciex API3000. The quantitation results for the parentcompound delivered by oral administration of the parent compound itselfor by its prodrug administered orally were used to calculate thearea-under-the-curve (AUC) values from time zeto to 24 hours (PO AUC0-24h). The comparison of the AUC values for the parent compound deliveredinto systemic circulation with that delivered by the prodrug allowedcalculating relative oral bioavalibility of the prodrug. See resultsprovided in Tables 22-26. When the AUC data for the parent compounddelivered by the parent compound itself after its intravenousadministration were available (AUC IV), it allowed calculating theabsolute oral bioavailability by dividing the PO AUC (0-24 h) for theprodrug by the IV AUC (0-24 h) for the parent molecule.

TABLE 22 Oral bioavailability of Isatoribine and its Prodrugs in MonkeysParent molecule Oral bioavailability and its prodrugs Structure incynomolgus monkey, % Parent molecule: 21  3 Isatoribine Prodrug: 24 7-9*Amino acid ester Prodrug: 93 80 Deoxy Prodrug: 77 28 6-Ethoxy Prodrug:79 21 6-Methoxy Prodrug: 84 14 Aminal Prodrug: 82  4 Aminal Prodrug: 8517 Dioxolenone *Average of multiple experiments at different doses.

TABLE 23 Oral bioavailability of Loxoribine and its Prodrugs in MonkeysParent molecule Compound Oral bioavailability in and its prodrugs No.cynomolgus monkey, % Parent molecule: 17 2 Loxoribine Prodrug: 45 96-Ethoxy Prodrug: 43 13 Deoxy

TABLE 24 Oral bioavailability of Imiquimod and its Prodrugs in MonkeysParent molecule Compound Oral bioavailability and its prodrugs No. incynomolgus monkey, % Parent molecule: 31 100 Imiquimod AUC (0-24 h) =9.0 Prodrug: 34 555 Pentyl AUC (0-24 h) = 50 carbamate Prodrug: 50 234Ethyl AUC (0-24 h) = 21.1 carbamate

TABLE 25 Oral bioavailability of Bropirimine and its Prodrugs in MonkeysOral bioavailability Parent molecule in cynomolgus and its prodrugsCompound No. monkey, % Parent molecule: 35 100  Bropirimine Prodrug: 48137* Deoxy Prodrug: 37 94 Ethoxy Prodrug: 36 33 Ethyl carbamate Prodrug:49  6 Pentyl carbamate *The oral bioavailability exceeding 100% may beassociated with gender differences since the parent compound was studiedin male monkeys and the prodrug was studied in female monkeys.

TABLE 26 Oral bioavailability of Adenine Prodrugs in Monkeys Parentmolecule Compound Oral bioavailability and its prodrugs No. incynomolgus monkey, % Parent molecule: 29 46 Prodrug: 65 1.3 MethoxyProdrug: 64 4.6 Ethoxy Prodrug: 62 0.7 Deoxy Prodrug: 54 9.7 Pentylcarbonate

Reduction of Gastrointestinal Irritancy

TLR7 ligand prodrugs of the invention also demonstrate unexpected andgreatly reduced toxicology effects, and in particular reduced GIirritancy.

The gastrointestinal (“GI”) tract is lined with substantial immunetissue (e.g., Peyer's patches, etc.). TLR7 ligand prodrugs offer theprospect of masking the active structure as the agent passes throughlymphoid tissue lining the gut, which should minimize activation of thistissue and thereby reduce GI irritancy.

Robins et al. have shown that elimination of the 5′-hydroxyl ofisatoribine nucleoside eliminates activity. See Robins et al., Adv.Enzyme Regul., 29, 97-121 (1989). Without being limited to anyparticular theory, it was hypothesized that blockade of this hydroxylsite by an ester substitution would similarly eliminate activity butallow transport in the systemic circulation, where the valine esterwould be cleaved and result in exposure to isatoribine.

We have found that the hypothesis was confirmed. Formal toxicologystudies of intravenously administered isatoribine and orallyadministered isatoribine and val-isatoribine were conducted in beagledogs. The toxicology results for orally administered isatoribine arefrom a study conducted by ICN/Nucleic Acid Research Institute.

We compared in the dog the oral toxicology of 21 and 24, and theintravenous toxicology of 21. We observed that the oral toxicology of 24was much more like intravenous 21 than it was like oral 21. Inparticular, the dose limiting toxicology of oral 3 was similar in natureto that of intravenous 21, and occurred at blood exposures that weresimilar to those observed after intravenous 21. In contrast, oral 21 hada different limiting toxicity (gastrointestinal lesions) and thistoxicity was observed at a dose lower than the toxic dose of eitherintravenous 21 or oral 24. Also, emesis was observed in dogs treatedwith oral 21 at doses lower than the dose of oral 24 that resulted inemesis. See Table 27. Other systems for assessment of emesis also areknown, such as in ferrets, allowing comparison of oral and intravenousadministration of compounds. See, e.g., Strominger N. et al., Brain Res.Bull, 5, 445-451 (2001).

In each case the compound was administered as a solution, by gavage orby intravenous infusion. Multiple parameters were assessed, as iscustomary in a toxicology study. In the studies providing higherpotential exposure to isatoribine, the plasma concentration ofisatoribine was assessed by a LC/MS method. The notable GI findings weregraded and are listed in Table 27.

TABLE 27 Effect on GI Tolerance in Dogs after Dosing of Isatoribine (21)or Val- Isatoribine (24) Ranked by Systemic Exposure (AUC) toIsatoribine in Toxicology Studies. Oral Val- Isatoribine OralIsatoribine IV Isatoribine Isatoribine equivalent Emesis Emesis Emesisapplied or GI or GI or GI dose AUC_(0-24 hrs) loose lesions or looselesions or loose lesions or (mg/kg) (μg · hr/ml) stool Irritation stoolirritation stool irritation 2.5 n.d Neg. Neg. 5 n.d. + Neg. 10 n.d. ++++ 8.1 11.4 Neg. Neg. 16 15.6 Neg. Neg. 12.5 19.5 Neg. Neg. 32 31.7 Neg.Neg. 25 42.8 Neg. Neg. 64 71 Neg. Neg. 130 75.3 + Neg. 50 87.8 + Neg.260 127 ++ Neg. 390 180 +++ Neg. 100 209 ++ Neg.

For orally administered isatoribine the principal findings were relatedto GI tolerability as measured by GI irritancy. The clinical signs notedin Table 27 were emesis and/or loose stools. These clinical signs weremore frequent in the 10 mg/kg group, and in one animal at this dose abloody stool was noted. Gross histopathologic evaluation of the GI tractnoted multiple, scattered red lesions on the intestinal mucosa in fourof eight dogs at 10 mg/kg, which on microscopic evaluation revealedcellular congestion and hemorrhage, as might be expected for an ongoinglocalized inflammatory process. The GI effects established the NOAEL as5 mg/kg.

Intravenously administered isatoribine resulted in emesis and/or loosestools as a common finding in dogs; this effect occurred atsubstantially higher applied doses than orally administered isatoribine.No lesions were seen in the GI tract either at necropsy orhistopathologic evaluation of tissues. The GI toxicity did not affectthe NOAEL, which was established as 12.5 mg/kg on the basis of otherfindings.

Orally administered val-isatoribine demonstrated a toxicology profilesimilar to intravenously administered isatoribine. At higher applieddoses, emesis and loose stools were observed. No GI lesions were found,although this was a focus of evaluation in this study. As forintravenously administered isatoribine, the NOAEL was established on thebasis of other findings. The correspondence of observed toxicity tosystemic exposures of isatoribine is of interest in this study; thethreshold of isatoribine AUC for observation of emesis and loose stoolsis similar for intravenously administered isatoribine and orallyadministered val-isatoribine (Table 27).

The data in Table 27 indicate that orally administered val-isatoribineprovides an improved toxicity profile over orally administeredisatoribine, and is consistent with the hypothesis that chemical maskingof the activity of isatoribine is afforded by chemically substituting anester at the 5′-hydroxyl position of the nucleoside. As illustrated inTables 9 through 14, it is possible to chemically mask any TLR7 ligandusing a variety of substituents. Engineering this substitution to becleavable upon entry into the body affords systemic exposure to theuseful activity of the compound without the limiting GI toxicity arisingfrom the anatomical structure of the GI tract. As illustrated in Tables22 through 25, it is possible to design the chemical substitution on amasked TLR7 ligand to be cleavable after administration. Thus, maskedTLR7 ligand prodrugs can be generated for any TLR7 ligand. This enablesadministration of doses that are substantially higher on a molar basisthan otherwise would be acceptable, with the result of greater efficacyand reduced side effects when compared to administration of the parental“unmasked” compound alone.

6.6 Oral Composition

Table 28 illustrates a batch formulation and a single dose unitformulation containing 100 mg of val-isatoribine.

TABLE 28 Formulation for 100 mg tablet Percent by Quantity QuantityMaterial Weight (mg/tablet) (kg/batch) val-isatoribine  40% 100.00 20.00Microcrystalline 53.5%  133.75 26.75 Cellulose, NF Pluronic F-68 4.0%10.00 2.00 Surfactant Croscarmellose 2.0% 5.00 1.00 Sodium Type A, NFMagnesium Stearate, 0.5% 1.25 0.25 NF Total 100.0%  250.00 mg 50.00 kg

The microcrystalline cellulose, croscarmellose sodium, andval-isatoribine components are passed through a #30 mesh screen (about430μ to about 655μ). The Pluronic F-68® (manufactured by JRHBiosciences, Inc. of Lenexa, Kans.) surfactant is passed through a #20mesh screen (about 457μ to about 1041μ). The Pluronic F-68® surfactantand 0.5 kgs of croscarmellose sodium are loaded into a 16 qt. twin shelltumble blender and are mixed for about 5 minutes. The mix is thentransferred to a 3 cubic foot twin shell tumble blender where themicrocrystalline cellulose is added and blended for about 5 minutes. Thethalidomide is added and blended for an additional 25 minutes. Thispre-blend is passed through a roller compactor with a hammer millattached at the discharge of the roller compactor and moved back to thetumble blender. The remaining croscarmellose sodium and magnesiumstearate is added to the tumble blender and blended for about 3 minutes.The final mixture is compressed on a rotary tablet press with 250 mg pertablet (200,000 tablet batch size).

6.7 Mucosal Composition

A concentrate is prepared by combining isatoribine, and a 12.6 kgportion of the trichloromonofluormethane in a sealed stainless steelvessel equipped with a high shear mixer. Mixing is carried out for about20 minutes. The bulk suspension is then prepared in the sealed vessel bycombining the concentrate with the balance of the propellants in a bulkproduct tank that is temperature controlled to 21° to 27° C. andpressure controlled to 2.8 to 4.0 BAR. 17 ml aerosol containers whichhave a metered valve which is designed to provide 100 inhalations of thecomposition of the invention. Each container is provided with thefollowing:

val-isatoribine 0.0120 g trichloromonofluoromethane 1.6960 gdichlorodifluoromethane 3.7028 g dichlorotetrafluoroethane 1.5766 gtotal 7.0000 g

6.8 Intravenous Composition

The intravenous formulation is prepared by reconstituting a compound ofthe invention with an appropriate liquid medium, such as water forinjection (WFI) or a 5% dextrose solution. A desired concentration ofthe intravenous formulation can be obtained by reconstituting anappropriate amount of a compound of the invention with an appropriatevolume of liquid medium. A desired concentration of the intravenousformulation provides a therapeutically effective amount of a compound ofthe invention to the patient, preferably a mammal, more preferably ahuman, in need of the intravenous pharmaceutical formulation andmaintains a therapeutically effective level of a compound of theinvention in the patient. The dose which is therapeutically effectivewill depend on the rate at which the intravenous formulation isdelivered to the patient and the concentration of the intravenousformulation.

For example, one vial containing a composition (e.g., 50 mg of acompound of the invention per vial) are reconstituted with a 5% dextrosesolution (14 ml of 5% dextrose solution per vial) yielding a total of 25mL of solution. The reconstituted solution is incorporated into adextrose solution in an infusion bag and q.s. to 50 mL, resulting in asolution containing 1 mg/ml of a compound of the invention suitable forintravenous infusion administration. The preferred concentration of acompound of the invention in the liquid medium, in the infusion bag, isabout 0.001 to about 3 mg/ml, preferably about 0.75 to about 1 mg/ml.

The foregoing has demonstrated the pertinent and important features ofthe present invention. Many modifications and variations of the presentinvention can be made without departing from its spirit and scope, aswill be apparent to those skilled in the art. The specific embodimentsdescribed herein are offered by way of example only, and the inventionis to be limited only by the terms of the appended claims along with thefull scope of equivalents to which such claims are entitled.

All references cited herein are incorporated herein by reference intheir entirety and for all purposes to the same extent as if eachindividual publication or patent or patent application was specificallyand individually indicated to be incorporated by reference in itsentirety for all purposes.

1. A method of treating a hepatitis C virus infection comprisingadministering to a patient in need thereof a therapeutically effectiveamount of a TLR7 ligand or a pharmaceutically acceptable salt thereof,wherein the TLR7 ligand is a imidazoquinoline analog.
 2. The method ofclaim 1 wherein the TLR7 ligand is a compound of formula Ic

wherein: each R¹ is independently H, or a substituted or unsubstitutedalkyl, alkenyl, or alkynyl, which may be interrupted by one or more O,S, or N heteroatoms, or a substituted or unsubstituted aryl orheteroaryl; R² is H, OH, SH, halo, or a substituted or unsubstitutedalkyl, alkenyl, or alkynyl, which may be interrupted by one or more O,S, or N heteroatoms, or a substituted or unsubstituted —O-(alkyl),—O-(aryl), —O-(heteroaryl), —S-(alkyl), —S-(aryl), —S-(heteroaryl),aryl, or heteroaryl; or a pharmaceutically acceptable salt thereof. 3.The method of claim 1 wherein: each R¹ is independently H or asubstituted or unsubstituted alkyl, alkenyl, or alkynyl; R² is H, OH,halo, or a substituted or unsubstituted alkyl, alkenyl, or alkynyl; or apharmaceutically acceptable salt thereof.
 4. The method of claim 2wherein the TLR7 ligand is

or a pharmaceutically acceptable salt thereof.
 5. The method of claim 1wherein the patient is human.
 6. The method of claim 1 furthercomprising administering a pharmaceutically acceptable excipient,carrier, or vehicle.
 7. The method of claim 1 further comprisingadministering an additional therapeutic agent.
 8. The method of claim 7wherein the additional therapeutic agent is an antiviral agent.
 9. Themethod of claim 1 wherein the therapeutically effective dose is 0.001 to100 mg/kg per day.
 10. The method of claim 9 wherein the therapeuticallyeffective dose is about 0.01 to 50 mg/kg per day.
 11. The method ofclaim 10 wherein the therapeutically effective dose is about 0.1 to 20mg/kg per day.
 12. The method of claim 1 wherein the TLR7 ligand isadministered parenterally.
 13. The method of claim 1 wherein the TLR7ligand is administered intravenously.
 14. The method of claim 1 whereinthe TLR7 ligand is administered orally.
 15. The method of claim 1wherein the TLR7 ligand is administered mucosally.
 16. A method oftreating a hepatitis C virus infection comprising orally administeringto a patient in need thereof a masked TLR7 ligand prodrug or apharmaceutically acceptable salt thereof, wherein the oraladministration of the masked TLR7 ligand prodrug achieves atherapeutically effective plasma concentration of the TLR7 ligand, andwherein the masked TLR7 ligand prodrug is an imidazoquinoline analog.17. The method of claim 16 wherein the prodrug is selected from a (a)carbamate moiety after conversion of a TLR7 ligand amine substituent,and (b) ester, ether, or aminal moiety after conversion of a TLR7 ligandalcohol substituent.
 18. The method of claim 16 wherein the prodrug ofthe masked TLR7 ligand is a compound of formula IIc

wherein: R¹ is H, or a substituted or unsubstituted alkyl, alkenyl, oralkynyl, which may be interrupted by one or more O, S, or N heteroatoms,or a substituted or unsubstituted aryl or heteroaryl; R² is H, OH, SH,halo, or a substituted or unsubstituted alkyl, alkenyl, or alkynyl,which may be interrupted by one or more O, S, or N heteroatoms, or asubstituted or unsubstituted —O-(alkyl), —O-(aryl), —O-(heteroaryl),—S-(alkyl), —S-(aryl), —S-(heteroaryl), aryl, or heteroaryl; R⁷ isindependently H or a substituted or unsubstituted —C(O)(C₁₋₁₈alkyl) or—C(O)₂(C₁₋₁₈alkyl); R⁸ is H, —OH, —O-(alkyl), —OCO₂(C₁₋₁₈alkyl),—OC(O)(C₁₋₁₈alkyl), or a racemic, L-, or D-amino acid group—OC(O)CHNH₂R¹; or a pharmaceutically acceptable salt or stereoisomerthereof.
 19. The method of claim 16 wherein R¹ is H or a substituted orunsubstituted alkyl, alkenyl, or alkynyl; R² is H, OH, halo, or asubstituted or unsubstituted alkyl, alkenyl, or alkynyl; R⁷ isindependently H or a substituted or unsubstituted —C(O)(C₁₋₁₈alkyl) or—C(O)₂(C₁₋₁₈alkyl); R⁸ is H, —OH, —O-(alkyl), —OCO₂(C₁₋₁₈alkyl), or aracemic, L-, or D-amino acid group —OC(O)CHNH₂R¹; or a pharmaceuticallyacceptable salt or stereoisomer thereof.
 20. The method of claim 18wherein the masked TLR7 ligand prodrug is

or a pharmaceutically acceptable salt thereof.
 21. The method of claim16 wherein the oral administration of the masked TLR7 ligand prodrugachieves an in vivo effective plasma concentration of the TLR7 ligandthat is 10% to 500% of the effective in vivo exposure obtained upon oraladministration of the TLR7 ligand alone.
 22. The method of claim 16wherein the oral administration of the masked TLR7 ligand prodrugachieves an in vivo effective plasma concentration of the TLR7 ligandthat is 50% to 200% of the effective in vivo exposure obtained upon oraladministration of the TLR7 ligand alone.
 23. The method of claim 16wherein the oral administration of the masked TLR7 ligand prodrugreduces undesirable side effects in a patient relative to the sideeffects upon oral administration of the TLR7 ligand alone.
 24. Themethod of claim 16 wherein the oral administration of the masked TLR7ligand prodrug reduces undesirable side effects by 50% in a patientrelative to the side effects upon oral administration of the TLR7 ligandalone.
 25. The method of claim 24 wherein the side effect isgastrointestinal irritancy.
 26. The method of claim 24 wherein theirritancy is hemorrhage.
 27. The method of claim 24 wherein theirritancy is lesions.
 28. The method of claim 24 wherein the irritancyis emesis.
 29. The method of claim 16 wherein the patient is human. 30.The method of claim 16 further comprising administering apharmaceutically acceptable excipient, carrier, or vehicle.
 31. Themethod of claim 16 further comprising administering an additionaltherapeutic agent.
 32. The method of claim 31 wherein the additionaltherapeutic agent is an antiviral agent.
 33. The method of claim 16wherein the therapeutically effective dose is 0.001 to 100 mg/kg perday.
 34. The method of claim 33 wherein the therapeutically effectivedose is about 0.1 to 25 mg/kg per day.
 35. The method of claim 34wherein the therapeutically effective dose is about 1 to 20 mg/kg perday.